You haven't said which airplane you are using but, the only thing of notice on that airport ( which I don't think it's related to the add-on you downloaded, since it doesn't seem to add/change any parking spots ), is that all parking spots seems to be a bit small, at least they are all too small for an A320-class airplane.
This can be fixed in two different ways:
- By customizing the airport (go to a runway, so you can open the menu there even if no parking spots are available) select all gates and click the small airplane icon, to adapt all selected positions to the wingspan of the airplane you are flying
- By enabling the "Ignore wingspan when parking" option in the GSX Settings, which will result in GSX always allowing to use any parking, without checking its size, globally.