Apple update mac Os Big Sur 11.2.1 quits and does not install

OK, I got with Apple Tech Support on chat again and the tech suggested erasing the drive and data after backing up by using command + R at start. I did that and then reinstalled the 'freshest' Big Sur which worked fine. I then reinstalled my apps and data from backup. Worked flawlessly. One thing though. I found it hard to believe that this problem was found during update testing and fixed. A bit disappointing that. Also, even being tech savvy taking such a drastic step makes me feel like I'm jumping out of a perfectly good airplane (something I won't do) and when I downloaded the chat to be sure I didn't miss anything I noticed it didn't download perfectly... something else for Apple to look at fixing. Luckily, being a bit 'anal' maybe, I copied the crucial part of the chat before downloading and saved it as a document which I printed out and also didn't need but it's something many would I'd think. Soooo... make sure you got the steps down before ending the chat or copy it out some other way besides downloading. It seems the numbered lines in the steps the tech sent were what did not print out which mostly gave me every other line. Example: "1. From the utilities window in macOS Recovery, select Disk Utility and click Continue." Came out in the download as a blank line and the 'Continue' which wasn't very helpful if you didn't know what you were doing already. Of course, there is always the Apple Store if you can get in! : ) Good luck! I hope the next update goes a bit more smoothly... this was like rebuilding the whole engine of the car from scratch when I only wanted to change the spark plugs. Make sure you know what you are doing before you attempt this!

Is there any chance there are AntiVirus software installed? If Yes, strongly suggest removing as per Developers Instructions. If No - disregard. Is one running behind a VPN - turn it off and try again. If No - disregard.

Yes there is, as well as a VPN that I use for security. Turning them off doesn't seem to help. Apple help advised that they've had problems with this update but that I could possibly be successful by downloading the update (Newest version of Big Sur, not labeled as an update) from the App Store. Which I did. 12GB or there abouts so be ready for a long meditative wait or run errands which I did instead. Installing the update this way with no anti-virus or VPN running (which I don't like doing) did not help in the slightest except as a tease... it 'locked up' at 52 minutes to go after getting to that point vvvveeeerrrryyyy slowly. So, no solution yet. I'll contact Apple help again sometime today if time permits.

Yes. Go to the App Store and search for Big Sur. It will come up.

That worked when I couldn't update before but not for 11.2.1. I always quits with 10 minutes to go without fail (so to speak). Looks like I'll be waiting for the next update instead. I have a 2019 refurbished MacAir which originally had Catalina before my update to Big Sur. I'm new to Mac and hope the updates aren't continually this grueling. It sucks nearly as bad as the old constant blue screens of Microsoft so far. I have plenty of space and good resources so the problem seems to be software.

Again - restart and hold Command + r immediately. Present to Recovery Mode and must have good internet connection and choose Reinstall macOS.

OR

This one is 100% dependant on Apple Servers / ISP Speed and stable, quick Internal connection - Restart hold Command + Option + r - Internet Recovery Mode - same options as Recovery only it will offer to Install the Latest Compatible version of macOS for this machine ( Not my favourite method )

Just some food for thought: unless you're using a true VPN tunnel, such as between you and your employer's or bank's servers, they are useless. Public VPN's are anything but private.  

Make sure you have a minimum of 35.5 GB of free space before attempting the download and install.

Are you trying the download and install from the Sustem/Software Update preference pane? If so try going to the App Store and download the installer from there. It's worked for many where the preference pane failed.

Restart in Safe Mode - Shift Key and try again. Hope and Patience

Extremely Welcome. The most important of all - the machine is working again. Thank you too :-)

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