Usually there is a dual valve; one side feeds the water fountain, and the other, the ice maker. Remove the valve by removing the one or two hex head screw(s). Disconnect the hose that feeds the ice maker and place the valve into a pan or bucket. Temporarily connect 115VAC to the terminals of the appropriate valve solenoid to see if water flows through it. If you get water in that manner, the problem is probably in the ice maker itself. If no water, replace the valve.