Good afternoon. This started to show up today.
That's not a GSX problem. In fact, GSX is telling you something useful, that the scenery you used has a bug, namely the "Parking isolated", which means you are parked in a spot that has no connections with the rest of the taxiway network, which is clearly a bug.
Previous GSX versions will just cause an error stopping the program, so it looked like a GSX error even when it wasn't. So, in order to be sure users won't assume this is some kind of GSX error, but it's instead an error of the scenery, we added an extra detection of this problem, issuing that message without going into panic mode.
Since the problem is not GSX, there's nothing you can do in GSX to "fix" this, the only solution is to fix the scenery. I checked the airport, and it's no wonder it doesn't work: it has only ONE parking, of the kind "Fuel", which is not connected to anything. There are no other parkings so, this looks like a bug in the default scenery, since it seem the airport is left unfinished.