With "any gate", you mean "every" gate ? Are they ALL really isolated ?
First, check the AFCAD used by GSX is the right one that comes with the scenery, I find hard to believe someone would make an airport with all parking isolated.
Assuming GSX loaded the correct AFCAD, you can open it with ADE, and check which parking spots are isolated. They are fairly easy to spot (and ADE will of course flag them as errors) and to "fix" what should have really been fixed by the scenery developer, you'll have to connect them to the rest of the taxiway layout using apron paths.