Hello,
I had the same problem the day before yesterday following an update, and today my entire library is visible again.
I specify that I could launch MSFS either by my direct shortcut from the SDK “fsdevmodelauncher.exe” without problem.
Try a restart of the computer or a reset of the MS Store.
Or,
1: Close the Microsoft Store app if currently open.
2: Press the Win + R keys to open the Run dialog.
3: Type WSReset.exe into Run, and click/tap on OK.
The WSReset tool resets the Windows Store without changing account settings or deleting installed apps.
4 A “command prompt” will now open without any message. After about 30 seconds, the command prompt will automatically close, and the Microsoft Store app will open.