Ensure that your UserCfg.Opt file located in your main installation Local Cache folder (probably here:
C:\Users\your user name\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalCache )
has an entry at the bottom marked Installed Packages Path, and this points to the correct location of the “Packages” folder.
The Packages folder contains the Official-OneStore and Community folders, which contain all your addons.