Investigate these four areas if your dishwasher is not working at all:
Your dishwasher may not be receiving any power. It is somewhat difficult to check for power at the plug outlet because the plug for a dishwasher is usually behind the unit. You should make sure all the circuit breakers of your circuit breaker panel are in the correct positions, or check to make sure no fuses of your house fuse panel are blown.
A properly functioning door switch will shut your dishwasher off when the door is opened. A defective door switch may not allow your dishwasher to operate at all. Examine the door switch and test it. If it is inoperable, it will have to be replaced.
It isn't very common, but it is still possible that your dishwasher's cycle selector switch has become defective. Test the switch to determine if it is the cause of your problem. Replace it with a new one if it is.
Your dishwasher timer will not function if its motor is defective. And if your timer is not functioning properly, then the dishwasher itself will not function properly. Test your dishwasher's timer motor, and if it is broken, you can replace either the entire timer assembly or just the timer motor.