I have run into a problem with the option to board passengers missing from GSX. All I get is Request Deboarding, Request Catering and Request Refuelling and that's it.
The issue of not seeing all the entries in the menu, which is not the GSX menu, but it's the standard Simconnect menu (so you'll see the same issue with every 3rd party application with a menu, not just GSX), has been discussed so many times on the forum and, of course, it doesn't have anything to do with GSX.
Instead, it's caused by some 3rd party airplanes, like the PMDG but others too, which use a very strange method to create their cockpit. If you look *very* closely on the top-left side of the screen when such airplanes are loaded, there's a single pixel "dot":
Which is in fact a whole 2D Gauge, that can even be resized, and it contains...an autopilot! This is probably confusing the sim, which is trying to resize the Simconnect menu based on the screen size, so the window starts too small, with some missing options.
Of course, the Simconnect menu window CAN be resized with the mouse, and the options are there. GSX doesn't have any control over this window, it's created by the sim and there's no way to ask for a specific size.