First check if water is entering the water pan under the evaporator. If not you will need to check your supply. Commonly we see the screen in the water solenoid valve plugged from poor water supply and dirty lines. On the lower left of the pan are 2 float switches. The front one is the one that controls the water fill at the start of the freeze cycle. The back one tells the machine to harvest. This is a sequence chart so you know what is on when.
Note that the pump does not come on till in the freeze cycle and the harvest float opens. Now if you have a dump valve problem, that never happens.