Pull out the impeller & shaft, and rinse them. Pull out the media & intake tube, and breifly plug it in to see if the impeller spins. If it doesn't, give it a little nudge with a slim object, a pen helps me with my fat fingers.
If it spins, unplug it, it probably isn't the impeller or shaft. Try filling it with a cup of water, no media or intake tube. Once again, plug it in breifly, giving it a nudge if it doesn't start spinning. If it spins, it almost certainly isn't the impeller or shaft.
Same thing again, with the intake tube attached, with no media, and a cup of tank water. No suction or spin means you are not attaching the intake tube properly. If it spins & pulls up water it is not the impeller or intake tube, unplug, add media, a cup of tank water, and plug it in. If it doesn't run this time you are installing the media improperly.