If its not shooting even if you manually load a bb in the hop up then its sounds like one of 2 things. 1 your not getting any seal at all from the piston head, that's the most likely source, or 2 the barrel is jammed. Sometimes its not the most complicated thing but the step You overlook that gets you. Take the barrel and hop up out and slide something down the barrel. If it doesn't come out the other end then there you go.