Whirlpool Dishwasher WDT710PAYM0. 5 years old. Won't start. When we hit the start button, we get 15 beeps, then nothing.

Rich,
At 15 years old you are probably going to find that parts will be limited in availability and expensive if they are available. With buttons not working, that sounds like probably a controller problem and that would be an expensive part. You would probably be better off putting your money into replacing the dishwasher. The average lifespan on a dishwasher is anywhere from 7 to 10 years, so you have your money's worth out of that unit. Hope this helps!

Bad touchpad user interface, is sticking in cancel mode causing unit to drain continuously... Replace both user interface and main control board due to software corruption

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Whirlpool Dishwasher Won Start

Drain issue, make sure the drain hose is ok

Make sure the dishwasher door is firmly closed, press and hold the start pause button for about 5 seconds, this will clear the cycle, The try selecting a wash cycle and push start.
See if this helps.

Alternate solution: Within 6 seconds, alternately press "heated dry" then "normal" buttons. Wait for all lights to come on and for the diswasher to finish washing the load.

Sounds like you might need a new Start button.

Did you try the power on button all the way to the left?

I have had the same problem with my the same dishwasher. The manual says that "the dishwasher has malfunctioned. Call service to check heater element". I called service and they are saying that replacing the heater element and possibly the electronic panel may be required. Total cost (part + labor) = $350-400!! I am very very upset with Whirlpool right now.