if all of your test point voltages test fine i would suspect the pin headers on the driver board and / or the cpu for the flippers not working.
also the pins in the housings that are on the wiring loom that connect the wires to these pins may need replacing.
when you press the start button can you here the flipper relay on the driver board (the board to the top right of the back box, the one with the big black heat sink on it)
