If the water supply cut-off valve for the dishwasher is all the way open and the dishwasher will continue to not fill, turn off the water supply, unplug the dishwasher, take off the fill line and take a look to see whether the screen in the water inlet valve is blocked.
If it has a lot of debris, swap out the water valve-do not just clean the screen, because small pieces slip into the valve body, stopping the valve from shutting close, and cause flooding. If the dishwasher still doesn’t fill, have a dishwasher service technician take a look at and repair the dishwasher.