It's not possible to help you with such a sparse description of the problem.
Using the configuration that comes with GSX for that airplane (use the RESET button in the airplane configuration to be sure you are using the configuration that comes with GSX ), jetways will surely work but, they cannot possibly work in every possible situation, since whether they work or not, depends not just by the airplane configuration, but also the parking spot, which means both how jetways are placed, but also your parking position on ground, which means understanding how the customization of the Stop Position in GSX works.