Why wont my HP PPSh-41 airsoft gun shoot?

I got this gun a few weeks ago, and I finally got a battery for it last week. I plug it in, load up the drum and wind it up and try to shoot it but it only blank fires(makes the sound, no bbs). The bbs will go up into the receiver and just sit there. If I open up the top of the gun and pull the trigger it wont always even make the noise. Did I get a bad gearbox/motor or is this something I can fix?