DIAGNOSIS The water inlet valve isn't opening or there's no water supply. The hum is the compressor running dry.
FIX First, ensure the water reservoir in the back is full. Pull the unit out, lift the lid on the rear tank, and fill it with potable water to the MAX line. Close the lid securely. The machine will not draw from a sink hookup if the internal tank is empty.
IF THAT DIDN'T WORK The water inlet valve solenoid may be clogged. Unplug the unit. Disconnect the short silicone tube from the valve outlet. Press a small funnel into the valve inlet and try pouring a cup of water through. If it doesn't flow, the valve is blocked.
HEADS UP Never use distilled water. The minerals in tap or filtered water are needed for the ice to eject properly. Using distilled water can cause ice to stick to the evaporator.