You don't say which airplane you are using.
If you are using an airplane already internally supported by GSX, try RESET its configuration with the airplane configuration editor, in case you made some error editing it.
If you are using an airplane that is not already internally supported by GSX, you must first create ( or find some place to download ) a GSX configuration for it, using the included airplane configuration editor, otherwise you just can't use it correctly.
Two Catering ending on the same door, usually means the catering doors are not configured correctly.