Apparently this was resolved a few days ago, but I am still having issues. I enter the app password into the Windows Security dialogue box, then it immediately pops back up again. I attempt to use the Contact - Microsoft Support page, and after I enter my problem, get this message:
'At least one of your devices is missing important updates. Before troubleshooting, use Windows Update to install the latest updates to see if this resolves the problem. DESKTOP-LN8MISI 0000000000000000 Update recommended'
so I then attempt to do updates, but get the message: 'We couldn't connect to the update service. We'll try again later, or you can check now. If it still doesn't work, make sure you're connected to the Internet.'