If your dishwasher doesn't work at all, check these:
Power from the house
there power getting to the dishwasher? This can be difficult to test,
because dishwashers are usually wired directly to an electrical
circuit, rather than plugged into the wall. But at least check for a
blown fuse or a tripped circuit breaker.
door switch is important because, if it's defective, the dishwasher
won't work at all. To reach it, you need to remove the control panel
cover, or sometimes the interior liner of the door. If it's defective,
you need to completely replace it.
the main wiring connection from the house, at the dishwasher, burns and
breaks the connection. If that's the problem, the wires must be
repaired/replaced as necessary. If that's not the problem, check the
wiring to the door switch, the wiring between the door and the lower
part of the dishwasher, and the wiring to the timer. Repair any broken,
burned, brittle, or defective wiring, using the proper appliance-grade
wire and connectors.
Timer or selector switch
it's uncommon, the timer or the selector switch may be defective. If
so, you need to replace the defective part, because neither of these
can be repaired.