External Hard Drive not Mounting

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?!

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

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

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.

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

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.....

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.

Mine does not show at all, only time it shows is if I hold alt at boot....has to be a driver issue

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. 😉

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.

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!

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

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.

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.

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!