Water Inlet Valve
If the refrigerator ice maker is not working the water inlet valve might be defective. The water inlet valve is an electro-mechanical valve. The coil can show good for continuity and still not let the water thru.
Low Water Pressure from House Supply
If the ice maker is not working the water pressure in the house might be too low. The water inlet valve which supplies water to the ice maker is designed to work with a minimum of 20 psi of water pressure.
Water Filter
If the refrigerator ice maker is not working the water filter might be clogged. Try changing the water filter.
Icemaker Switch
If the refrigerator ice maker is not working, check the icemaker switch. This switch frequently gets turned off by accident. If the switch is turned on but the ice maker still doesn't work, check the switch for continuity with an Ohm meter. Replace as needed.