Hello Umberto,
I use FSUIPC, RAAS pro, ...
But, I have tested (and had exactly the same problems) without thoses modules and with the community older empty (except 2 folders for gsx).
In my msfs2020 community folder there is 2 shortcuts (pointing to C:\Program Files (x86)\Addon Manager\MSFS\fsdreamteam-gsx-pro and fsdreamteam-gsx-world-of-jetways):
fsdreamteam-gsx-pro
and fsdreamteam-gsx-world-of-jetways
My MSFS 2020 is installed in a dedicated directory c:\simu (so outside c:\program files (x86) ).
GSX is installed in the default c:\program files (x86) (I have also tested an installation in c:\simu)
I have updated all .NET libraries, microsoft visual basis c++
Maybe is somewher a problem of rights management ? ?? I really don't understand where is the problem.