restart pc , also check that xbox app is up2date, if you start msfs with a “short link” then try to start directly / re-new the short-link.
See also topics like:
Where Start as admin is mentioned as workaround…
May be you find other hints:
https://forums.flightsimulator.com/search?q=access%20to%20the%20specified%20device%20path%20or%20file