71 Replies
      Latest reply: Aug 16, 2017 1:02 PM by Socramedina RSS
      KawKawKins Level 1 Level 1 (0 points)

        Since updating to macOS Sierra, my Seagate 1TB Harddrive isn't being read or mounted by my Retina MacBook Pro (2014) ... It appears in Disk Utility but not in Finder or on the Desktop ... In Disk Utility I cannot do anything but format it which I DO NOT want to do .. Any suggestions or help?!

        • Re: External Hard Drive not Mounting
          Tinsleyjf Level 1 Level 1 (0 points)

          I really hope you find an answer to this. I'm having the same issue. My entire iTunes library is on the portable drive...

          • Re: External Hard Drive not Mounting
            Stempnakowski Level 1 Level 1 (0 points)

            Similar issue with my Western Digital external USB drives. None mount, but they are also not seen by Disk Utility.  They do show up in the System Information utility as being seen on the USB bus, but don't show as HDs.

            • Re: External Hard Drive not Mounting
              Joachim_Joe Level 1 Level 1 (0 points)

              I have this issue too with any external hard drive, they do not show up in the Disk Utility. This issue, is not a Seagate-specific issue.

              • Re: External Hard Drive not Mounting
                BiggStuu Level 1 Level 1 (0 points)

                Same here, all drives appear on the bus in the system, but only the seagate mounts.  Terrible part, the missing drives are my Time Machine and Downloads.  Ugh. So literally, I cant update my apps, use iTunes, backup my machine, etc. I'm thinking about rolling out of the beta.

                 

                • Re: External Hard Drive not Mounting
                  MohamadAlwazzan Level 1 Level 1 (0 points)

                  same here, none of my USB external drives are connecting or visible anywhere. i guess we have to wait until the next beta

                  • Re: External Hard Drive not Mounting
                    intellexi Level 1 Level 1 (0 points)

                    Same here with WD My Book

                    • Re: External Hard Drive not Mounting
                      Fillman39 Level 1 Level 1 (0 points)

                      I have a 1TB Seagate (FAT32) and 4TB Seagate (Mac OS Extended), and the 1TB works perfectly fine under USB while my 4TB just shows up in disk utility

                      • Re: External Hard Drive not Mounting
                        DrDubya Level 1 Level 1 (0 points)

                        I have 2 external drives that do not mount.

                        And my apple usb wired keyboard doesnt work either.

                        MacBook Pro (Retina, 15-inch, Mid 2015)

                        • Re: External Hard Drive not Mounting
                          Slcarter Level 1 Level 1 (0 points)

                          My WD external hard drive will not mount and does not show up anywhere. I also can't go back to an older OS because my backup is on my external HD. All my files are on external HD so iTunes is useless and everything else. I hope they fix this soon.

                          • Re: External Hard Drive not Mounting
                            ChrisSW Level 1 Level 1 (0 points)

                            My WD My Passport USB3 drive is not appearing but my Transcend SSD on USB 3 is being seen.

                            • Re: External Hard Drive not Mounting
                              seth9341 Level 1 Level 1 (0 points)

                              I have two Buffalo USB 3 drives and a WD my passport usb3 that are also not mounting

                              • Re: External Hard Drive not Mounting
                                seth9341 Level 1 Level 1 (0 points)

                                I just updated to the newest beta release as of 2016.07.20 at 14:00 and my USB drives are back!!!

                                • Re: External Hard Drive not Mounting
                                  Slcarter Level 1 Level 1 (0 points)

                                  Yes the new update has fixed the USB issue. everythng seems to be running ok even with this late 2011 model a little slow but its to be expected.

                                  • Re: External Hard Drive not Mounting
                                    Inspirations Level 1 Level 1 (0 points)

                                    Drobo does not mount, finder does not see it, but de  drobo dashboard can see it.

                                    • Re: External Hard Drive not Mounting
                                      psciandra Level 1 Level 1 (0 points)

                                      I am having this issue with a Western digital My Passport external on my macbook 12" Retina.  I am on latest Sierra beta, have tried from another thread installing and uninstalling WD turbo drivers.  My drive is still not available.  If I hold alt on startup the drive is shown but when I boot to main drive and login drive never shows.  My timemachine backup, etc is on this drive.....

                                      • Re: External Hard Drive not Mounting
                                        HStriepe Level 1 Level 1 (0 points)

                                        I have a similar issue. Various drives (usually one) do not show up on the Finder desktop after boot, but are actually mounted in /Volumes - often as read-only. Oddly I need to force unmount with diskutil before being able to remount them.

                                        • Re: External Hard Drive not Mounting
                                          nexkulit Level 1 Level 1 (0 points)

                                          So far, this works every time - http://www.seagate.com/as/en/support/downloads/item/ntfs-driver-for-mac-os-master-dl/ - even now that I've upgraded to OS Sierra.

                                            • Re: External Hard Drive not Mounting
                                              ggrigorian Level 1 Level 1 (0 points)

                                              Thanks @nexkulit! this solved my problem as well! I was having the same issue with my 1TB Seagate drive not showing up in Finder. But it was in Disk Utility and grayed out and I wasn't able to mount it. Downloaded the suggested utility from Seagate and rebooted and it's back!

                                              • Re: External Hard Drive not Mounting
                                                LoriCristen Level 1 Level 1 (0 points)

                                                Thanks so much this fixed my problem straight away!!

                                                • Re: External Hard Drive not Mounting
                                                  dmcverry Level 1 Level 1 (0 points)

                                                  I tried this but the dmg file I D/L from Seagate says it's damaged so I'm still stuck.

                                                   

                                                  I've tried to D/L it numerous times & even from different browsers. Always the same - the file is damaged

                                                  • Re: External Hard Drive not Mounting
                                                    manuelobico Level 1 Level 1 (0 points)

                                                    Thanks nexkulit! This solved my problem right away, I was having the same issue with my 1TB Seagate Backup Plus Portable drive not showing up in Finder and being unable to mount it although it showed in Disk Utility grayed. Downloaded the suggested utility from Seagate, rebooted and bam it's back as if nothing had happened!

                                                    • Re: External Hard Drive not Mounting
                                                      easymuon Level 1 Level 1 (0 points)

                                                      This solved my problem

                                                      • Re: External Hard Drive not Mounting
                                                        wolfshades Level 1 Level 1 (0 points)

                                                        Thank you very much nexkulit! Though I had Paragon NTFS on my system already, I downloaded and installed Seagate's version and voila - my drive showed up. A check on volume said it was "dirty" (whatever that means), so I quickly copied the contents back to my iMac HDD and am in the process of doing a secure erase on the stupid thing, right before I throw it in the garbage. I will NEVER buy a Seagate peripheral ever again. This thing has been a nightmare.

                                                         

                                                        Even during the copying it managed to mess things up and reboot my system. Took forever to get the thing mounted again. I hate Seagate with a passion now.

                                                        • Re: External Hard Drive not Mounting
                                                          dcp2798 Level 1 Level 1 (0 points)

                                                          This did not work for me.
                                                          I spent some time searching and came up with this solution that did work:

                                                           

                                                          Opwn the finder preferences:
                                                            Finder > Preference
                                                            In the general tab reset the default values:
                                                            1. Show these items on the desktop (uncheck all)
                                                            2. New Finder Windows show (All My Files)

                                                            3. Open folders in tabs instead of new windows (check)

                                                           

                                                          Then I unplug and plug back in my HD.

                                                           

                                                          I then Reset System Management Controller SMC:

                                                          Shut down

                                                          Press and hold

                                                          shift, ctrl cmd(option) + power

                                                           

                                                          When I booted and set my finder preference back to show all external HD's. everything worked and I have not had a problem since.

                                                          Now even my Tech Tool emergency disk is performing correctly.


                                                          iMac Late 2013 27"

                                                          Sierra 10.12.4

                                                        • Re: External Hard Drive not Mounting
                                                          Paula Jay Level 1 Level 1 (0 points)

                                                          My Samsung HDD with all my photos on was read only after updating to Sierra as was the brand new HDD I own.  I used the new HDD to back up Time Machine and this seemed to open the HDD to read & write.  This then enabled me to copy all the photos to the new HDD.  I then repeated the process on the original HDD.  The Time Machine process erases the HDD which seems to open it read & write again.

                                                          • Re: External Hard Drive not Mounting
                                                            csb2767214 Level 1 Level 1 (0 points)

                                                            I reinstalled the Seagate drive from the site and it's now showing. For other drivers, might suggest reinstalling their driver from their site as well

                                                            . Just a suggestion, I thought about downgrading back to El Capitan but too complicated for me. Good luck!

                                                            • Re: External Hard Drive not Mounting
                                                              catebligh Level 1 Level 1 (0 points)

                                                              Yes, reinstalling the drivers for my Seagate and WD drives solved this problem.

                                                              • Re: External Hard Drive not Mounting
                                                                kaihsu Level 1 Level 1 (0 points)

                                                                My problem is a Transcend hard drive that does not automount at startup. If I unplug the USB and plug it back in, it mounts and everything is fine.

                                                                • Re: External Hard Drive not Mounting
                                                                  bob321 Level 1 Level 1 (0 points)

                                                                  I had the same problem with Samsung D3 station external hard drive. I've tried reinstalling drivers and everything several times allready, it just won't mount. Disk Utility shows nothing either. Frends pc worked fine with that drive, and also my LCD TV mounted that drive.

                                                                   

                                                                  Finally solved the issue with $2 USB extender cable, I did a picture:

                                                                  http://rebane.planet.ee/flash/usb_ex.jpg

                                                                   

                                                                  After I pluged it up, MacOS mounted my Samsund D3 station right away, now everything works and I don't know actually what was the real problem. I think it's something to do with SS to USB3 cable. I have a iMac 2013.

                                                                  • Re: External Hard Drive not Mounting
                                                                    mmautino Level 1 Level 1 (0 points)

                                                                    I have 2 6 TB WD My Book Duo connected to my 2011 iMac 27", using thunderbolt cables and ports.

                                                                    One contains my Time Machine and the other ALL MY RAW and JPG PHOTO files...

                                                                    Since I upgraded to Mac OX Sierra, they randomly fail to mount.

                                                                    Restart does not help, changing cables does not help.

                                                                    I cannot see them in Finder, Disk Utility or System Information.

                                                                    Sometimes, one or both of them randomly mount, and in that case I have run a diagnostic of each drive using the WD tool app that came with the drives and they are fine. If running the diagnostic with Disk Utility, they unmount and dissapear again.

                                                                    After the computer goes to sleep and Time Machine attempts to run a backup, the Time Machine drive will dissapear.

                                                                     

                                                                    Please Apple, take care of this,...

                                                                    Is this an Apple attempt to force us out of external drive and into very expensive iCloud storage?

                                                                    • Re: External Hard Drive not Mounting
                                                                      maurerc Level 1 Level 1 (0 points)

                                                                      Similar problem with the released verion of 10.12.1. External drives plugged into a USB3 hub have ceased to work after "upgrading" from El Capitan.

                                                                      • Re: External Hard Drive not Mounting
                                                                        seralyse Level 1 Level 1 (0 points)

                                                                        For hours, I was trying multiple restarts and even installing the latest update, but my hard disk was still unreadable.

                                                                         

                                                                        Reinstalling the Seagate drivers worked like magic!

                                                                        • Re: External Hard Drive not Mounting
                                                                          HungryLikeTheWolf Level 1 Level 1 (0 points)

                                                                          My situation:

                                                                          WD My Passport Ultra 2T

                                                                           

                                                                          I formatted it Mac OS Extended (Journaled, Encrypted) to use with Crash Plan as a back up drive.  It works fine until I eject the disk and put the computer to sleep.

                                                                           

                                                                          When I plug the drive back in before or after waking the computer, the OS does not see the drive.  It is not visible in Disk Utility.  I have to perform a reboot in order for the disk to mount.

                                                                           

                                                                          Computer:  iMac 27-inch, late 2013

                                                                          OS: Sierra (10.12.1)

                                                                          • Re: External Hard Drive not Mounting
                                                                            kettlekekkers Level 1 Level 1 (0 points)

                                                                            i own 2 external hard drives,  (not very new) but worked fine with all other OSX,  and PC<    update has made them completely unusable., they dont mount, they dont apper in disk utility, or system information.

                                                                             

                                                                            not much to my delight all responses from apple and the hard drive manufactureres are very typically ;conflicting, each blames the other, and there is yet to be a solution.

                                                                             

                                                                            most likely now forced to buy an new expensive upto date hdd.

                                                                              • Re: External Hard Drive not Mounting
                                                                                Rexster Level 1 Level 1 (0 points)

                                                                                I am running the latest version of Sierra and I have also run into a mounting problem with my external hard drives.  The problem for me (just to reiterate) is that sometimes a drive will mount and sometimes the same drive will not mount (which means show up on the desktop as it should when it mounts correctly).  I do not believe that there was any operating system release that 'fixed' this issue.  When I reboot my computer (2012 Mac Mini), the hard drives that previously would not mount will mount correctly.  This happened just a few minutes ago.  I had two hard drives that mounted and four that would not mount.  After rebooting, all the drives mount and work properly.

                                                                                 

                                                                                To those who are worried about their data, I believe the data on your external drives is intact and can be retrieved as long as the disk wasn't formatted or erased using disk utility. Don't panic!  Turn off the external drive, disconnect from your computer, and reboot.  Hopefully this will resolve some fraction of the problems people have experienced in this thread.

                                                                                 

                                                                                I have had this problem intermittently for over a year.  My machine stays on 24/7 and I think that either the hardware or software gets into a state where mounting fails.  I haven't figured out a way to isolate the problem, but maybe its related to when the external drives were originally formatted.  In my case, these drives are all several years old although they were correctly formatted Mac OSX journaled before they were initially used. 

                                                                              • Re: External Hard Drive not Mounting
                                                                                arjun_vkumar Level 1 Level 1 (0 points)

                                                                                Facing the exact same problem. Lights are on when mouse is connected and the harddisk is connected but not being detected. Sometimes it works and sometimes it doesnt. I need to have a permanent solution for this as it is very inconvenient.

                                                                                  • Re: External Hard Drive not Mounting
                                                                                    Dwain Level 1 Level 1 (0 points)

                                                                                    Thunderbolt drives are also affected.  Unable to be recognized on boot.  Only recognized after boot on internal drive, and cannot be switched to boot from the OS System Pref.  Interesting they would release a build

                                                                                    that defeats their prized Thunderbolt/USB3 external drive ability.  Have seen this before on mac 2011 and earlier, with no solution offered.  Wait for the next Beta update to potentially resolve this with no feedback on 'cause'...

                                                                                     

                                                                                    Suggest you and those affected revert to the prior build, which did not have this problem...

                                                                                      • Re: External Hard Drive not Mounting
                                                                                        Dwain Level 1 Level 1 (0 points)

                                                                                        Can you please try setting the following boot-arg and see if resolves your issue: sudo nvram enable-legacy-orom-behavior=1

                                                                                         

                                                                                        Worked for me to release the "Option" boot menu to external drive selection.  Hope this helps someone else also...

                                                                                    • Re: External Hard Drive not Mounting
                                                                                      nsthankiya Level 1 Level 1 (0 points)

                                                                                      I have a similar issue with Mac Mini late 2012 running 10.12.2 Beta (16C53a) Seagate 5TB external USB 3.0 will sporadicly not mount unless the system is rebooted. This HD is connected directly to USB 3.0 on the mini not through a hub. It worked fine under 10.11 and 10.10. I have a number of other 1 & 2TB external USB 2.0-3.0 drives WD & Seagte that all mount fine. I've sent numereous feedback reports to Apple but still no sollutions.

                                                                                      • Re: External Hard Drive not Mounting
                                                                                        bergertime Level 1 Level 1 (0 points)

                                                                                        I only recently updated to 10.12.1, and have found this problem as well with my Seagate 1TB USB HDD (not SS). The drive is mountd and visible in Disk Utility, but not in Finder. At least on several occasions, re-launching finder has fixed the problem. Still haven't worked out the exact scenarios under which the problem occurs or the Finder re-launch fixes it.

                                                                                        • Re: External Hard Drive not Mounting
                                                                                          ctraq91 Level 1 Level 1 (0 points)

                                                                                          10.12.4 beta - since updating, external drives do not have correct permissions, and do NOT show up in disk utility!!

                                                                                          • Re: External Hard Drive not Mounting
                                                                                            MusicalBarry Level 1 Level 1 (0 points)

                                                                                            A partial solution which at least makes an external HDD usable again.

                                                                                             

                                                                                            I have a Rugged Triple FW/USB3 drive which wouldn't mount on Sierra (from 10.12.1 to 10.12.3) on a Mid-2010 MBP.  Works perfectly on other machines running Yosemite - tried re-formatting on Yosemite but Sierra still wouldn't mount the drive whether encrypted or not.

                                                                                             

                                                                                            Eventually re-formatted as exFAT on Windows 10 whereupon it mounted on Sierra.  Then used Disk Utility on Sierra to re-format as Mac OS Extended (Journaled, Encrypted) and all seems well.

                                                                                             

                                                                                            Unfortunately had to copy the data to another drive using Yosemite so it's not a solution if you have essential data which you're unable to copy off by other means.

                                                                                              • Re: External Hard Drive not Mounting
                                                                                                donb Level 1 Level 1 (0 points)

                                                                                                I haven't had any thunderbolt issues on Mac Pro, have had USB mounting problems with HDDs, not flash drives. I have an Apple Thunderbolt Display and when using it's USB ports, I don't have any issues. I'm running 10.12.3, no betas. Maybe if you can run the USB though a thunderbolt hub as a workaround at least. Still should have been fixed months ago.

                                                                                              • Re: External Hard Drive not Mounting
                                                                                                Doctor_Huw Level 1 Level 1 (0 points)

                                                                                                As of February 2017, a Samsung T3 external SSD is recognized erratically. Sometimes, my MacBook Pro OS X Sierra (10.12.3) recognizes it. Sometimes it doesn't. This is true for both USB ports. I replaced the drive. Same problem with the replacement.

                                                                                                 

                                                                                                Nothing has been done that might damage the drive, the cable, or the port. For example, with the MacBook powered down, I plug in the drive, start up. No problem. I then shut down and restart. Now the drive is gone. Disk Utility doesn't see it at all. Power down, switch to second USB port, power up. Now the drive is recognized. But at some point, the drive will also disappear from that port.

                                                                                                 

                                                                                                Repeatable but unpredictable.

                                                                                                 

                                                                                                This suggests a problem with USB connectivity under Sierra.

                                                                                                • Re: External Hard Drive not Mounting
                                                                                                  Nanayo Level 1 Level 1 (0 points)

                                                                                                  can you please help me unlock my iCloud to

                                                                                                  • Re: External Hard Drive not Mounting
                                                                                                    roadparc Level 1 Level 1 (0 points)

                                                                                                    I had the same problem with a Western Digital 2TB My Book Studio.

                                                                                                    It showed up in disk utility but not in finder.

                                                                                                    What I did was right click in the external HD that appears in disk utility and from there you can click show in fnder!

                                                                                                    It seems like the partition had a hidden attribute. I was in a hurry so I just grab the HD in finder and add it to my favorites bar in the left side of finder.

                                                                                                    I think that I need to research about the hidden attribute but for now I can work and access to my HD.

                                                                                                     

                                                                                                    I hope this works for anyone having the same problem.

                                                                                                     

                                                                                                    Edit:

                                                                                                    I also found how to unhide the partition. Just use the chflags mettod.

                                                                                                    Open terminal and type:

                                                                                                    "chflags nohidden "

                                                                                                    With a space at the end and drag and drop the drive from finder to terminal and hit enter.

                                                                                                    Use what I explain earlier to get access to your HD in finder using disk utility shorcut

                                                                                                     

                                                                                                    Thank you

                                                                                                    roadparc

                                                                                                      • Re: External Hard Drive not Mounting
                                                                                                        Desktop-Laptop Level 1 Level 1 (0 points)

                                                                                                        I had the same problem too, but with a USB 3.0 External Western Digital 3TB  HD, My Passport For MAC.

                                                                                                         

                                                                                                        While running a Late 2009 Mac Desktop, with Yosemite 10.10.5,  I was attemping to back up with Apple's Time Machine application my Desktop Computer onto my USB 3.0 External Western Digital 3 TB Hard Drive, My Passport For MAC.

                                                                                                         

                                                                                                        The 3 TB HD icon wouldn't show up on either the Finder window or Computer screen, on my Desktop computer, but would show up within the Desktop computer application, Disk Utility, on the left side of it's window.  There it would allow me to select Verify and Repair,  but once the process ran its course, a window would pop up to say an error has occured: "Couldn't open disk" or "The disk couldn't be unmounted".  Now, I know the 3 TB HD was running because I could feel it the rotation of the hard drive and I could see that it's exterior white light was on.  So here's how I was able to bring back!  Since I had access to an additional computer, with the latest Operating System, Sierra 10.12.3., I plugged the USB 3.0 External Western Digital 3 TB Hard Drive, My Passport For MAC. into a laptop.  As some time had passed, 15 to 20 minutes, while I was discussing this issue over the phone with Apple Care, yet before we were able to implement any Apple Care solutions,  I opened up the Finder window and sure enough there and on the computer screen, was the 3TB My Passport For Mac!  Recap: From my experience, find a newer second computer, even a friend's, who's running the latest operating system. (Allow some time) for the USB 3.0 External Western Digital 3TB  HD, My Passport For MAC to be recognized by the computer, a laptop in my case.  Check back later with it's Finder window or Computer screen and with some luck, it appears!  You're back in business.  If not, although I never got around to it, I'm sure Apple Care will have some suggestons.  Good Luck and Keep me posted!

                                                                                                          • Re: External Hard Drive not Mounting
                                                                                                            urbananimal Level 1 Level 1 (0 points)

                                                                                                            I'm having the same issue. The delay is that the connected disk is running fsck in the background before it shows up, which can take some time. If you open a terminal window, cd to /var/log and "tail -f fsck_hfs.log" (or another if not hfs) you'll see this running.

                                                                                                             

                                                                                                            That said, my fsck never completes successfully, which is an issue that disk disk mounts read-only.

                                                                                                        • Re: External Hard Drive not Mounting
                                                                                                          sjpapa2 Level 1 Level 1 (0 points)

                                                                                                          Well had the same problem. But found solution!
                                                                                                          One of my USB-SATA interfaces does not work. This is correct no way to mount.

                                                                                                           

                                                                                                          But a WD external disk mounted immediately. One other USB-SATA interface I have also mounted immediately.
                                                                                                          It seems Sierra does not have all drivers for all USB-SATA devices installed.

                                                                                                          • Re: External Hard Drive not Mounting
                                                                                                            maximveksler Level 1 Level 1 (0 points)

                                                                                                            Same here, WD hard drive. Almost shipped it for warrenty repair becaseu I assumed the drive was faulty. Then plugged into a Windows PC and it mounted.

                                                                                                             

                                                                                                            No issues appears again. No work arounds, reboot of the OS donesn't help.

                                                                                                             

                                                                                                            **** !

                                                                                                              • Re: External Hard Drive not Mounting
                                                                                                                qtxtn Level 1 Level 1 (0 points)

                                                                                                                I did your suggestion while sipping on vodka: plugged the external drive to a Windows laptop... replugged it to my Macbook Air.. and voila, external drive is showing on the desktop.

                                                                                                                 

                                                                                                                It may have been the vodka, though. But seriously, thanks for this suggestion. No downgrading to El Capitan needed!

                                                                                                              • Re: External Hard Drive not Mounting
                                                                                                                maximveksler Level 1 Level 1 (0 points)

                                                                                                                I have a solution.

                                                                                                                 

                                                                                                                1. Open terminal
                                                                                                                2. Run some commands to find the "id" of your drive
                                                                                                                3. Ask the system manually to mount your drive.

                                                                                                                 

                                                                                                                Step 1

                                                                                                                 

                                                                                                                Open Applications > Terminal (the black/white empty screen where you can write text into it)

                                                                                                                 

                                                                                                                Step 2

                                                                                                                 

                                                                                                                Run the following command:

                                                                                                                 

                                                                                                                diskutil list |awk '/external, physical/,/^$/' | awk ' /[1-9]+[0-9]*:/ { print $3, $6 } '
                                                                                                                
                                                                                                                
                                                                                                                
                                                                                                                
                                                                                                                

                                                                                                                 

                                                                                                                In my case this outputs:

                                                                                                                EFI disk2s1
                                                                                                                m disk2s2
                                                                                                                Recovery MB
                                                                                                                
                                                                                                                
                                                                                                                
                                                                                                                
                                                                                                                


                                                                                                                And the drive which I'm interested in is "m", so my "ID" is disk2s2

                                                                                                                 

                                                                                                                Step 3

                                                                                                                 

                                                                                                                Run the following command

                                                                                                                 

                                                                                                                diskutil mount disk2s2
                                                                                                                
                                                                                                                
                                                                                                                

                                                                                                                 

                                                                                                                Your drive should now be mounted.

                                                                                                                 

                                                                                                                Theory

                                                                                                                 

                                                                                                                For the technical explanation of what is going on: The kernel is able to load the usb device, but (I assume) that the system event messaging subsytem fails to handle the new usb storage device detected event for whatever reason (process restart, wrong key name.. what ever.. it's random in nature). therefor kernel sees the device but user space is not, because device is not mounted. The above fixes the loss of the system event notification by doing it manually.

                                                                                                                • Re: External Hard Drive not Mounting
                                                                                                                  edie Level 1 Level 1 (0 points)

                                                                                                                  I'm experiencing a similar problem. I have a G Drive Mini 1T 0G02577 which is failing to mount. This is connected to a MacBook Pro (Retina, 15-inch, Late 2013) which I have recently updated to Sierra 10.12.4. It may be coincidence but I have only had this problem since updated the OS, until then the disk was mounting and running without any problems.

                                                                                                                  I can see the drive in Disk Utilities and also in ‘About this Mac > System Preferences > Hardware > USB', but it will not mount. I have seen that some other users have experienced similar issues with portable drives failing to mount since this OS update so I am wondering if this may be the problem?

                                                                                                                  I desperately need to retrieve the data on the disk. If anyone has any advice I would be so grateful of any help resolving this.

                                                                                                                  • Re: External Hard Drive not Mounting
                                                                                                                    mechyserra Level 1 Level 1 (0 points)

                                                                                                                    This was usefull for me many times!  http://www.tuxera.com/products/tuxera-ntfs-for-mac/

                                                                                                                    • Re: External Hard Drive not Mounting
                                                                                                                      kiza Level 1 Level 1 (0 points)

                                                                                                                      It has happend to me as well, what i did , i had older mac with old system and i just run older disk utility repear disk permission and did fix the problem.

                                                                                                                       

                                                                                                                      New systems can not do the same job......

                                                                                                                       

                                                                                                                      Lacie drive do have some issues if you format HD as Ex fat.....

                                                                                                                      • Re: External Hard Drive not Mounting
                                                                                                                        patrickbaltieri Level 1 Level 1 (0 points)

                                                                                                                        Follow these instructions: https://discussions.apple.com/thread/7904838?start=0&tstart=0

                                                                                                                         

                                                                                                                        After this, my problems with external usb/thunderbolt drives were solved.

                                                                                                                        • Re: External Hard Drive not Mounting
                                                                                                                          Wkwkwkwkk12 Level 1 Level 1 (0 points)

                                                                                                                          why my verbatim plug in macbook pro touch bar  is working but cannot read my flash drive but before it can read my flash drive? The flash drive is not showing in finder and disk utility but when i charging via the verbatin it is work

                                                                                                                          • Re: External Hard Drive not Mounting
                                                                                                                            gadgetricks Level 1 Level 1 (0 points)

                                                                                                                            Yeah this discussion is useful

                                                                                                                             

                                                                                                                            https://discussions.apple.com/thread/7904838?start=0&tstart=0

                                                                                                                             

                                                                                                                            1. Relaunch the Finder.

                                                                                                                            The discs may be mounted and available; however, if the Finder is having troubles displaying them then it may appear as though the discs are not mounted. Press the Option key and right-click the Finder icon in the Dock, and choose "Relaunch".

                                                                                                                            2. Change the port.

                                                                                                                            Sometimes there are differences in the USB ports on the system, which result in power or speed differences that can result in external devices not being recognized properly. Try each USB or FireWire port available on your system (use FireWire 400/800 adaptors or conversion cables if necessary) to see if that helps. You can also try this when booted into Safe Mode, to see if any third-party plug-ins or nonessential features of OS X are contributing to the problem.

                                                                                                                            3. Plug in power adaptor (if available).

                                                                                                                            Some external drives come with optional power adaptors (especially smaller and more portable drives). If you have one, try plugging it in so the drive is not reliant upon bus power. Low power can definitely prevent a drive from working properly.

                                                                                                                            4. Avoid daisy-chaining.

                                                                                                                            When troubleshooting USB or firewire devices, unplug all except for the problematic device (and your keyboard and mouse, of course) and plug it directly into your system. Do not route it through the keyboard or a USB/FireWire hub, as this is yet another source for incompatibilities and problems.

                                                                                                                            5. Try a different connection type.

                                                                                                                            Some devices have both USB and FireWire ports, so use each of them to see if the device works. If it does with any of the ports, then you know the device is probably not to blame and can focus on troubleshooting the bus/connector that is causing issues.

                                                                                                                            6. Run general maintenance.

                                                                                                                            Give your computer a once-over maintenance run. Reset the PRAM and SMC, followed by booting into Safe Mode and clearing caches and performing a permissions fix with various maintenance utilities (Cocktail, Yasu, OnyX, just to name a few). Then boot normally and reboot again (the first boot will fill caches and be a little slower than the second) before trying the problematic external drive.

                                                                                                                            7. Drive problems

                                                                                                                            Last but not least, there may be problems with the drive itself, which can be caused by a number of issues including power or connection interruptions without properly unmounting the drive (a frequent occurrence for external drives). For information on how to tackle partition and volume problems,see this article.

                                                                                                                             

                                                                                                                            Hope this will be helpful.