Cannot upgrade the W10 version from 21H2 to 22H2.

It would help if you had the error message or code generated by the upgrade. Windows will also generate a report and place it on the desktop.

1. Check that your current version of Windows is fully updated and has no further updates queued (it should not be trying to upgrade when you shut down/restart).
2. Check Apple Software Update next. Some Macs have received driver and software upgrades that should be applied before a service build update.
3. Temporarily remove non-essential third-party hardware and software (i.e. anything outside of Apple and Microsoft). Don't remove the drivers for built-in hardware, but do remove drivers for printers, add-on mice, add-on storage (some external drives use nonstandard backup software or management utilities) and the like.
4. If needed, run an error check (CHKDSK) against the Windows volume. Open a Command Prompt as admin and enter: chkdsk c: /f. Answer Y to the prompt. Restart in Windows.
5. Use Disk Cleanup (CLEANMGR) to "take out the trash", if needed
6. Try the installer again.

If you still get an error, consider backing up your data and obtaining a fresh copy of Windows 10 for a do-over. For that extra bit of caution, make sure you're running the latest macOS that you can run, so that your Boot Camp Assistant can get the most recent driver pack for your Mac. If you are then able to upgrade, you should enroll for the update extension as soon as possible.

Good luck,

--Nate

It is certainly not the Mac's age, my last Bootcamp is on a "mid-2012" MacBook Pro that received two updates today: "Cumulative Update for Windows 10 version 22H2 for x64 (KB5065429 and KB5066198)". There again, update history shows that it has been on 22H2 since October 2022. I wonder if the Recovery option in Update & Security might be worth trying. As Windows 10 is at the end of its support time, it is certainly worth signing up for the Security Updates until October 2026 when these are offered.

What kind of error message do you receive?