I have found that if I press Esc key on keyboard then boarding/deboarding will commence.
Also like the member above, the view keys are not working while in waiting but after pressing Esc key, view keys start working again.
That is very strange. What the Esc key does, is to send a "Stop", then a "Start" Simconnect command to all connected add-ons, including GSX.
GSX correctly needs to use it, so it won't try to needlessly send commands that won't be listened by the simulator when you are in one of the menus. But normally, a Start command is sent also when you first load a flight, in the exact same way, and the code in GSX that reacts to it is exactly the same as after pressing the ESC key, there's no difference whatsoever and GSX doesn't know if a Start came because you started a flight, or because you pressed Esc twice.
The most likely explanation for this, since we cannot obviously reproduce it ( and if it really was a GSX problem, thousands of users would have reported it so far ), is that you have another add-on that is interfering with this, altering the started/stopped state of the simulator, and for some reason pressing the ESC key reset it back to normal. Maybe something that is stealing the main window focus.