Xbox X - CTD by start game. I have completely uninstalled and re-downloaded and re-installed, but the game still crashes on startup. I don’t know what to do anymore.

Support didn’t help at all. The problem persisted. I joined the beta yesterday. Problem solved! In the beta version, MSFS can be run from both accounts I have in XBOX. So I believe the account verification issue has been fixed in the current beta version.