You are not supposed to use custom passenger waypoints for the animated part of the jetway. They never work, because the animated part is in different places depending on the airplane door height and the airplane position. The only thing you can use custom passenger waypoints for, is the static part behind the jetway, the bridge.
If the airport has been bought on the MS Marketplace, you must enable the SU10 Navdata API in the GSX Config panel, otherwise the airport data can't be read, meaning jetways cannot be associated to a parking spot, because GSX can't read the parking spots from encrypted airports, unless you enable the Navdata API.