I was in the exact same situation.
It started 10 hours ago but when I tried to start it this morning I got an error asking me to set the disk and it wouldn’t start.
When I looked at the MSFS page in the xbox app, I saw the error “stranded” and it looked like there might be a problem, so I uninstalled the xbox app.
When I reinstalled it, I got an error that it could not be installed due to a problem on the server side, but when I tried again, the installation succeeded and when I started the xbox app, the error was gone and MSFS would also start.