Regarding your problem...here's what I do in the proper order:
1. Make sure the switch on the wall is turned on to supply power to the dishwasher.
2. Take the lower panel off where the wires connect and measure the incoming voltage to the dishwasher to ensure you have 120 volts.
3. If voltage is present, the inner door must be removed to expose the controls and door latch switches so you can check them. There is a Maytag Tall Tub Manual in this forum, so use it to see how to do all this. My best guess will be that your control board is likely bad if there is indeed power at the bottom.