In my installation I have a folder called XboxGames, which contains a folder called Microsoft Flight Simulator.
That is the one I had accidentally moved to another drive on the same PC…then I had a really long wait as well until MSFS started.
There is something strange with MSFS regarding the installation location. It doesn’t look at the registry like other programs do.
Some of the Beta testers have mentioned similar issues when a new version comes out for them to test and they do not direct the PC to the proper location.