To fix this issue, you need to install the XBOX APP (BETA) on your PC, following the steps type in the search bar "Microsoft Flight Simulator 2020", it'll then ask you to install depending on if your Microsoft account you bought it on is signed in to the Xbox App on your pc, it'll then download the digital ownership and allow you to access the official launcher of Microsoft Flight Simulator 2020.
If you're still having problems, reply back and I'll gladly give more fixes, if I know how of course lol.
hope it works!