I faced the same problem today. Here’s what I did and everything seems okay now.
- Exited MSFS
- Opened Xbox game bar to see if I could log out there. Didn’t find a logout option, and hence quit the app.
- Opened the Microsoft store and logged out of my account.
- Restarted the PC and ran MSFS. It gave me the “please insert disc” dialog.
- Exited MSFS and opened Store and logged in there.
- Opened MSFS and all was well!
Hope this helps.