EGCC is the only airport where it only gives me the option to "Select Parking Facility"
Not a very precise description of the problem. GSX will show the "Select Parking facility" in EVERY airport, when you are not parked on a gate. Since you don't say *where* you were located when you opened the GSX menu, it's not possible to say if this is a problem or simply the normal behaviour.
it then lists "Parking 1, 2 or 3." No options to park at a gate or anything else...
See above, that's normal, since that airport has 3 groups of parking spots of the "Parking type", GSX show the groups, which will THEN allow you to select a specific parking into a group. Again, this is the standard behaviour when you are outside of a parking spot.
If you were in a parking spot, chances are the AFCAD of the scenery has a problem, and perhaps GSX has reverted to the default AFCAD, which will likely not match parking positions.
To check which AFCAD is in use by GSX, open the "Customize parking positions" from the Couatl menu, it will tell which AFCAD is being read for the scenery in use.