If you only used the installer to install, there's no reason whatsoever why GSX wouldn't work, unless you FSX installation has issues, like Simconnect not working, of conflicting older Simconnect versions installed by other add-ons that use older version ( GSX use exactly the one from Acceleration pack ).
So, either your FSX install has issues, preventing GSX to run, or it's the antivirus/firewall so, again, repeat the one and proved method that works:
- Uninstall GSX. At the end of the installation, reply YES to the question "Do you want to remove the Addon Manager?"
- Configure the antivirus to the whole Addon Manager folder to the antivirus Exclusions.
- Be sure no firewall might possibly block the updater.
- Reinstall GSX, and if you have enough space on C: drive, just accept the default folder, which is perfectly fine. But any other folder/drive will work. The worse choice would be, instead, installing "inside" the main FSX folder, don't do that.
- When you restart FSX, pay attention if it ask permission to run the program ( the security question with the yellow shield ). If you don't see it, we already have a problem.