For some reason your add-ons.cfg is created in a wrong format. Maybe one of your add-on rewrote that.
Could you please try the following. Rename it for something else and P3D by the next start will generate a new one.
It is here: AppData\Roaming\Lockheed Martin\Prepar3D v5
To open your appdata open a folder browser in the search type %appdata% and enter.
Some success, see attachment! We're getting close now:
-I renamed both add-on.cfg in appdata\roaming\Lockheed Martin\Prepar3D v5 and in \programdata\Lockheed Martin\Prepar3D v5
-I disabled all other addons from the directory documents\Prepar3D v5 Add-ons
-I restarted P3D and let it rebuild the add-on.cfg. Only both LHS directories remained in documents\Prepar3D v5 Add-ons
-Let the LHSimulationsSceneryConfigurator run again
-Restarted P3D again
So it seems indeed something was wrong with on of the add-ons.cfg files
I will add now some other addons now and check if it works still