I Just had a log in error. I have a Dell Precision 7710 mobile work station with the Anniversary Update. I turned on the machine and tried to log in and got:


We can't sign into your account
This problem can often be fixed by signing out of your account, then signing back in. If you don't sign out now, any files that you create or changes that you make will be lost.

Logging out and restarting did not work. I shut it down, undocked (it is a Thunderbolt Cable Dock), and then restarted. Luckily it was back to normal log in. I shut down docked, and booted and it was normal log in again.

Not sure what happened. Hope the issue does not come back.

I read online this happened to others, but cannot find a cause or fix (other than restarting) and wondering if anyone knows why this happened.