I have Windows 10 configured so that I log in to my Windows account, not my Microsoft account.
Last Friday (23 September), I awoke to find that Windows had updated itself, rebooted, and was waiting for me to log in.
But the log-in screen had been changed. I didn't want that.
I logged in, using my Windows account password, and Windows said "Welcome", indicating that I had logged in to my Windows account successfully.
But my desktop had been changed to the standard Windows 10 default desktop. I didn't want that, either.
And Windows immediately said that it couldn't log me into my MICROSOFT account, so it was logging me onto a temporary (Microsoft?) account.
I tried to log in to my Microsoft account using my Microsoft password, but Windows responded with the same message.
I thought that maybe I should try to log OUT of whatever temporary Microsoft account I had been logged in to and then try to log in to my Microsoft account, just to make sure I could. But it turned out I wasn't logged IN to any Microsoft account.
So I rebooted. But the same whole sequence of events happened again. Except that this time, there was a DIFFERENT log-in screen.
So I rebooted again, and the "Can't log into Microsoft account" message did NOT reappear.
But now, every few minutes, Windows is saying:
"You need to fix your Microsoft account for apps on your other devices to be able to launch apps and continue experiences on this device."
I don't HAVE any other devices!
How do I make this stop?