See if the fill tube is full of ice, blocking the flow of water. It's the tube the water comes out of to fill the ice mold on the back inside the freezer.The water inlet valve on the back of the unit where the water supply comes in can have a slow leak and will cause ice to buildup and block the fill tube. Disconnect the ice maker line from the valve and watch to see if it has a slow drip. It doesn’t take much to eventually block the fill tube.
The valve can leak because of sediment in the water preventing it from closing or low water pressure.