I have a Maytag QuietSeries

Question

I have a Maytag QuietSeries 300 dishwasher. My original problem was with the control panel lights not coming on. Another repair website recommended replacing the circuit board. We replaced the board, but it did not solve the problem & the dishwasher would not work. Replaced the control panel. Lights come on, but when the start button is pushed "21" flashes on the time display. What do I do?