"No parkings" seems strange, because it means GSX has read the AFCAD correctly, but couldn't find any parking spots, or maybe *usable* parking spots, meaning they should be properly connected to the taxiway network.
Another possible reason, is that the AFCAD is not self-contained, meaning it's not a complete AFCAD but, it just overrides something of the default one, so some information is in the default AFCAD and other in the one that comes scenery. OR, if the data is split through multiple AFCADs supplied with the scenery, which is basically the same issue. GSX do not support such configuration, which is not very common (although FSX itself can handle it), since most of the scenery developers (especially commercial ones), usually supply a self-contained AFCAD.
If someone could send me the AFCAD in use (indicated by GSX in the parking customization dialog), we can have a look at it.