The Maytag top loader washer MAV7750BGW started to fill at the beginning of the washing cycle then stopped. Could not get it to do anything on any other cycle steps. Electrical supply OK. Managed to get it to start filling again but it stopped again almost immediately.

It sounds like you have a lid switch problem. Check your the lid on your washer and see if it's not bent towards the middle. Often as things get sat on top, it will bend and not allow the switch to make contact. The washer doesn't do anything but fill when the machine thinks the lid is open. Try bending the middle of the lid back to where it is straight.