On 11/1/21 I ran Norton 360 LiveUpdate. At the end, it reported that a patch needed to be installed. I clicked the "Install now" button (which usually doesn't work, but I thought I'd try). It closed applications successfully, and apparently installed the patch. At the end of the day, I shut Windows down.
The next day I booted up normally, but noticed after a few hours that Microsoft Store wasn't working correctly. The "View Reliability History" in Control Panel showed many Critical Event entries like this:
WinStore.App.exe Stopped responding...
the first one appearing around boot-up time on the day after the patch install. Ah well, maybe time will fix the problem.
But same thing the next day, after another round of shutdown/start.
At that point, on a hunch, I decided to restart Windows, since this doesn't do the phony "fast shutdown/fast start" stuff, but instead does a true shutdown. Poof, Microsoft Store worked great as soon as the computer was back up.
Is there a chance that Norton 360's patch installation on 11/1/21, the day before I noticed the problems with Microsoft Store, somehow left certain applications (like Store) in a "weird state"? After all, on-line patch installation does do that "Closing applications..." step.
I'm running Windows 10 Pro 20H2 on a 64-bit Dell desktop of recent vintage, with Norton 360 version 22.21.10.40. Microsoft Store is version 12107.1001.15.0.