Here is the parts breakdown
Replacement parts for WHIRLPOOL GU940SCGB3 DISHWASHER | AppliancePartsPros.com

I would start with the overflow switch (Item 30 in Section 3).
Check that the float (Item 32 in Section 3) is not stuck in the up position.
This switch is wired in series with the water valve and will kill power to the valve if not closed.

Next I would check for power (120 volts) across the water valve (Item 16 in Section 3) when it should be filling.
If there is power then either the valve is toast or the filter screen on the input side of the valve is clogged. Remove the valve from the unit and check/clean the screen. Do not permanently remove the screen from the valve as it is there to keep crud out of the valve which could hold it open and cause a flood.

If there is no voltage across the valve then check across the valve and switch combo.
If there is voltage there, remove power from the unit and check the switch for continuity, should be 0 ohms. It may be toast.
If there is no voltage then check the wires from the control. If they are OK then odds are that control board (Item 2 in Section 1) is shot.