You are on a PC right? See if you can somehow uninstall the Xbox app and reinstall, sounds like that’s the culprit.
Here’s link on how: https://flightsimulator.zendesk.com/hc/en-us/articles/4412971935762-Microsoft-Store-Uninstall-and-reinstall-the-Xbox-app
Or if you have a spare hard drive, put it in your PC, load Windows 7 (assuming you have that disk), then do the upgrade to W10… maybe that can be a test then do all the Sim installs fresh, get it working then clone over to your existing drive or a faster bigger drive if you want.