There is another repair function that I don’t think you have tried yet. Inside the XBox App, select My Library, select the MSFS that is shown as installed. In the top right of the resulting window select the … (more) option, select Manage, select Files, select Verify & Repair.
The XBox App repair and the Windows Apps repair might be doing the same thing, but the XBox App has produced a quick repair for me recently.
Good luck