I have a fully functional Mamiya 645 Super with a hand winder. Works like a champ. Bought a Power Winder N from KEH, the Battery check gives a Red light, when I hook it up to the camera, you press the shutter button down and you get the indicators in the AE finder and the camera fires, but then it doesn't wind. if I turn the switch to start, it winds a bit, but it won't fire. I put the manual crank back on, and the crank turns about 1/2 a turn, then I can fire the camera again.

I've got new batteries in the camera and the winder.

What am I doing wrong?