As explained many times already (too many times to count, really, there's even a blue highlight on the manual), GSX doesn't control, doesn't affect, doesn't change, is not affected by, anything related to jetways.
They continue to work (or not) as they always did. Installing GSX won't change anything about how jetways operate. Nothing in GSX can change anything related to jetways in any scenery, they are entirely and totally separate.
About the REST of the services, that are controlled by GSX, your issue might simply be that you are trying to use an unsupported airplane without configuring it first, as explained here:
http://www.fsdreamteam.com/forum/index.php/topic,10619.0.html