[iKliiu]

I have a version 2 gearbox thats completely new, I dropped it in to my M4, yet it work. I've charged the battery (also used a multimeter to check if the current was actually getting passed through the gearbox, which it was). I've also checked the motor, it works fine. But when I put the motor into the grip, plug the battery in and pull the trigger, nothing happens, as if the motor was stuck. I've also tried adjusting the motor, it didnt do anything either.
Any suggestions on what is wrong and how to fix it?

Thanks