there is an entry in the aircraft.cfg that prevents the gear from being lowered at the higher speeds. so slow down to like 230kts or something like that and the gear should work fine

I believe the default 747 does the same...no gear until you reach an "approavable" app speed and flap setting...no?
Actually the default 747 doesn't have this problem, it's any plane that uses "Fly by Wire" and i think the 777 series is fly by wire. Also it's like the deafult A321 the landing gear won't come out until you have reached like 200 knots and I THNK you also should have any degree of flaps down.
Also try the maunel pump command in FSX
Step 1. Place landing gear lever/switch in the down position
Step 2. HOLD ctrl+g it manually lowers the gear. KEEP holding in that command till the lights in the cockpit are green for the wheels.
Hope it works