As explained so many times, it's impossible to provide any kind of help with a so sparse description of the problem, so I'll need to proceed with some assumptions.
When the passenger boarding is simulated, it always happens on a parking with a jetway, where the jetway couldn't be detected as docked. You haven't said anything about which scenery is, if it's default or 3rd party, and if it's 3rd party, if it's bought on the Marketplace and you haven't said if you are using the SU10 Navdata API option in GSX, and all of these matters A LOT, when jetway detection is concerned.
- When the SU10 Navdata is Disabled ( default, using the airport cache ), GSX can usually detect jetways fairly reliably, because it matches their position in the .BGL with their position in the scene so, assuming the jetway really docked ( if it didn't, there's nothing GSX can do to change or improve that ), the only possible reason why the jetway couldn't be recognized, is that GSX loaded the wrong .BGL, either because of its priority, or because an add-on scenery failed to include the proper DeleteJetways command or because the .BGL was too big, or because it's from a Marketplace airport, so there was no way to read the .BGL at all.
- When the SU10 Navdata is Enabled, while GSX won't have any problems reading the airport data itself ( parkings, taways, runways ), because it's coming from the sim directly with a Simconnect call, since the Navdata API doesn't yet contain data about the Jetways position ( we have been asking for this since the first SU10 Beta came out ), GSX needs to do some heuristic to search for jetways, looking at their names. Some cases cannot just be solved this way, because if a parking spot contains two jetways, a "real" one and a "fake" one, which have exactly the same name and with the fake one that might even be the closest one to the user airplane position, if GSX is lead to pick up the "fake" jetway, it cannot detect if it has docked, so Passengers boarding will only be simulated and will go very quickly, like in any other case in which the jetway has been detected as not Docked.
That's why we still have the option to not use the Navdata API because, even if it's clearly better in the vast majority of situations, it still lacks some crucial data about the jetways position that are important for GSX to create passengers, so we can only hope the requested data will be added to a future SDK update.
I suggest reading this post which clearly explains in detail what we are missing from the SDK and, of course, cast your vote so it will be at least discussed:
https://forums.flightsimulator.com/t/sdk-q-a-ask-your-questions-here/552074/11?u=umberto67
