I was in the SU6 Beta. Installation was and has always been in a separate directory C:\MSFS2020 directory.
Upon starting the game, it told me there was a mandatory update in the MS Store. Went there, it states it’s downloading but nothing is happening - except that I see the directories in
:\Users\YourUsername\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\
have timestamps from 10 mins ago.
And
:\Users\YourUsername\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalCache\Packages
which used to contain files and directories is now empty.
Stuck here with no further activity at the moment.
Edit:
I killed the Store task. Rebooted and launched the Store again and went to the MSFS entry. Launched the game and it wanted to install ~95GB in the path above, but I was able to point it to my existing installation directory. At which point, it proceeded to launch normally. It’s all good.