Unable to Download Big Sur 11.2.1

The same issue failed to download. My internet is fine.
iMac 27, 2017

Same issue since 11.1 updates. I went to a service center just to have it installed with 11.2. Now, I can't update to 11.2.1.
I am using M1 Macbook Air that I purchased last month.

Same problem here on Macbook Air 2017

Unable to Download Big Sur 11.2.1 Solved
I did then try the internet recovery (option+command+R) at startup.
After a view minutes I got to the recovery screen and selected reinstall Big Sur, there it will download and install the latest compatible OS. So if you running Big Sur 11.0.1 and update 11.2.1 is available it will install 11.2.1 for you.
I did not loose any off my files or data averting is back just the way it was, the whole process takes time depending on your set-up and internet speed for me it was about 2 hours.
I hope this will help, It worked for me on a MAC Book Pro early 2015

Had this problem for weeks. (2020 13" M1 MacBook Pro)

What finally worked:

1. turn off macbook

2. hold power -> keep holding -> boot options (safe mode) -> select options

3. "Reinstall" Big Sur

Installed 11.2.1 over existing Big Sur install (keeping Users intact, i.e. not a clean install)

Same problem with a 2019 Macbook Pro. Easiest fix for me has been to clear caches, close all apps, shut down and restart, update downloaded no problem.

Using MBA M1 16GB 1TB. Latest update to Big Sur. 11.2.1
As recommended I tried to download update through conventional method - About, Software update.
After 5 tries I rebooted but not in safe mode.
Tried again and was successful.
It appears the network is just congested. Silver Sparrow!

Good luck

I was having the same issue and after about 3 reboots I was able to install the latest update. Although I must mention that before being able to update I had previously disabled bitdefender antivirus.

Tried Safe mode, PRAM reset

What worked for me:
Boot into Recovery

Start Security Startup Security Utility and set Medium Security. See https://support.apple.com/en-us/HT208198

Reboot and upgrade.
Go back and set High Security (if required)

Same issue. I have tried all suggestions stated here and still no joy. Come on Apple get your finger out and fix the issue.

I had the same issue on my MacBook Air (early 2015). I deleted a few larger applications like iMovie and bingo!

It seemed to need more than three times the stated update size. For guidance I've 13GB free on the disk now.
Hope this helps

I kept getting an error message that my internet connection failed when trying to download the update. I have a MacBook Air 2019 and this is what worked for me after trial and error:

1. Cleared cache and cookies in browser

2. Restarted in safe mode

3. While in safe mode, I deleted old files and apps that I don't use and this seemed to move the download along

4. I kept my Mac charging while it was downloading and installing

It took about 20-25 minutes to complete.

try to edit the rospkg/os_detect.py file, the file path will be in the error output
edit the line 363

from :

Code Block  python
def _osx_codename(major, minor):
    if major != 10 or minor not in _osx_codename_map:
        raise OsNotDetected("unrecognized version: %s.%s" % (major, minor))
    return _osx_codename_map[minor]

to

Code Block  python 
def _osx_codename(major, minor):
    return 'big sur'

I have the same issue with my retina 12 (2017) tried connecting to a different network because at first i think it was my wifi not working but after trying several times (safe mode too) and seeing this forum I think there might be something else going on.

would love some help thanks.

This happened to me before when Big Sur first released. The update works after uninstalling any app that uses software that doesn’t belong to Apple (Google Chrome, Microsoft Word, Etc).