Since the last update of the "Standalone Addon Manager" i get this message
The problem is not caused by the update, it's caused because you must have disabled GSX from its menu.
Could you please check if you disabled GSX, maybe when trying to get rid of the problem ? It can be done with the GSX menu, by choosing the "Disable addon" menu option.
Of course, if you disabled it, it would not be possible to access the GSX menu now, but that setting is saved in this file:
%APPDATATA%\Virtuali\Couatladdons.ini
See if you have these lines near the start:
[gsx]
disable = 1
and change it to
[gsx]
disable = 0
Then start FSX again.
P.S.
I removed your post by mistake, that wasn't intentional, but I kept the quoted part.