GSX has been purposely designed not to activate any of its services, unless you call for it, in order not to possibly create issues with other products that might always happen and you wouldn't be able to fix if GSX started automatically as soon as you positioned your airplane on a gate.
On arrival, it's a non-issue, because if you select your destination gate in GSX as soon as you are landed, it will be immediately populated with the crew.
You can obtain the same result when departing, by using the FSX Go To Airport menu to position on the Active runway first, then open GSX menu to select a parking (which will populate it with the crew), then open it again, select the same parking again and choose the "Just warp me there" option.