There are several possibilities. The most common is probably low refrigerant. Are you sure the compressor is actually running? If it just humms for 2 or 3 seconds, it may be a burned out compressor. That would be bad news. Take the side panel off and turn the unit on. If the compressor comes on and runs, the small line coming from the compressor to the condensing coils, (the thing that looks like a radiator) should be hot to the touch if it is not you are probably low on refrigerant. There is a safety switch that shuts the compressor off if you are low on freon. The compressor would "short cycle". That is it would come on and off and not every minute or so. That is bad for the compressor and won't make ice either. Also if you don't get a constant flow of water it might do the same thing. There is very little the average person can do to an ice machine as complicated as this one. Check your water flow, check the air flow throught the radiator like coils near the compressor. Other than that you need a refrigeration mechanic to check the freon pressures.