compressor running constantly but ice not dropping
Sometimes the ice gets stuck in the tray -- there's supposed to be a heater that melts the outside of the ice so it can be pushed out. 

Check if there is ice in the icemaking tray.

When this happens, I use a hairdryer to loosen the individual crescents, and push them out with a wooden spoon handle. The cycle usually resets and starts producing ice normally afterwards.