If you have the GSX menu under the "Addons" menu, then you can forget about antivirus, libraries, etc. If the GSX menu is there, it means the software IS working.
The reason why the GSX menu doesn't open only a certain airports, is almost invariably caused by an AFCAD in conflict. You can check which AFCAD is in used by GSX by opening parking customization menu, and see if the AFCAD used by GSX is the one that comes with the scenery.
Also, some of these sceneries might allows switching between different AFCADs, by renaming them. Due to the way GSX detects scenery changes, it cannot detect a file rename, otherwise it would have to scan each and every file at each start, making it very slow but, instead, it only checks the folder last modification date, and this doesn't change after a rename, which means, if a scenery file has been renamed, you MUST select the "Restart and rebuild the airport cache" option from the Couatl menu after the renaming took place.