If you got this error message and can't get in to MSFS, here is what I did.

Windows Update - Reboot computer.
Make sure you signed out of Xbox completely.
Delete Xbox apps from Default Apps - Reboot computer.
Download new Xbox app, search - Xbox Windows 10 PC
Sign in to existing Xbox account.
Run MSFS update.
What I have noticed since the update the spinning loading circle doesn't go away the lower right corner of the screen. Let me know if you too experiencing the same please?