Hi,
Please refer to the steps below to check.
https://answers.microsoft.com/en-us/xbox/forum/xba_wowpc-xba_gowpc/microsoft-flight-simulator-2020-asks-to-insert/2d37a3f4-ef0d-4473-9928-97731c46757f
Also I find some information below about Flight Sim 2020 may related this issue.
Microsoft Flight Simulator
Known Issue: Some users seeing a "Please insert the Microsoft Flight Simulator disc" error when launching the game on Windows 10.
Workaround: In order to play the game digitally on Windows 10, you will need to have the Digital Ownership
File installed as it is required to grant the necessary permissions to play. If you already have this file installed and are running in to this error, please uninstall and reinstall this file only and this should resolve the issue. There is no need to
uninstall the entire 127+GB base game files. Uninstalling this small 10MB file is all that will be needed.
Hope this helps and please help to accept as Answer if the response is useful.
Best Regards,
Carl