Jetways in MSFS are NOT controlled in any way by GSX. GSX will just sent a trigger (as if you used a custom key command) to toggle the jetway but, the rest is completely handled by MSFS itself, and whether it will work or not, depends only by how the jetway has been modeled and placed, and the relationship between the jetway and the parked airplane.
GSX can only receive some data from Simconnect about the jetway docking status. If GSX says there aren't any jetway attached, even if they "visually" seems to be ok, it's because normally, when a jetway is fully attached, the position of the jetway head almost perfectly matches the position of the door exit, even if sometimes the jetway docks too high or too low.
GSX checks this distance and, to prevent showing passengers "walking in the air", which users might assume it's a "GSX bug" (when the real problem was the jetway partially docked), it won't show passengers if the distance between the jetway head and the door is larger than 1.5 meters, which is about the average length of a passengers walking stride.
It might be possible, also, that a problem in the scenery results in GSX receiving wrong data, for example if a jetway is associated to the wrong parking spot but, in some cases, MSFS will dock a jetway from a nearby parking by itself, and this will clearly confuse GSX, because it sees you are parked in a certain gate, but the jetway for that gate hasn't docked and the nearby one has ( but it shouldn't ).
