I logged into my PC today (from locked screen). There was no problem. I attempted to run my apps, and I received bad gateway errors from the calls to my flows that load initial data. I then had a Windows notification (a fly-in on the bottom right - Win 10) that said that my login credentials needed in some way revalidated (I forget the actual wording, it went kind of quick). It did appear to be a windows notification, not powerapps.
I logged out of windows, then on first attempt, I was locked out. I had to contact my IT department to get unlocked. I have a non-expiring password, and there was nothing on their side that indicated anything more than just a normal lockout from invalid attempts.
I logged in, and my apps ran fine. No problems at all.
Now, I have another user haivng similar symptoms. Same bad gateway error. It could be something else, but I suspect not since its acting similarly.
Anyone else???