First things first, have you changed the battery? I'm sure leach wouldnt of sent you a duff hopper.
so change the batterys, then tap the back plate (above the power button) once the loaders on. It should spin.
also, a reloader wont just spin like you thought, because its sound activated it needs to pick up the sound before it will feed. (so gun shoots, loader feeds)
I also think im right in thinking that if its a halo then it will spin when its on because the eyes wont be picking anything up in the feedneck.
but change the batterys (even if a fresh set have just been put in) and report back.
GOGO!