Your log shows GSX is working perfectly fine, it found the correct airport you are in, but it didn't the data it requires from the Navdata API.
In order to be usable by GSX, an airport should have at least 2 parking spots, a runway, and taxiways connecting these. It seems the scenery developer might have excluded all taxiways, without providing his own, so all parking spots are isolated. Only solution is to alert the developer, because it's a scenery problem that will have issues with AI as well, not just GSX.