What should I do if the oven won't start?

First, check if a fuse in your home has blown or the circuit breaker has tripped—replace the fuse or reset the circuit breaker. If that's not the issue, unplug the microwave oven and plug it back in to address any power surge. Make sure the 3-prong plug is fully inserted into the wall outlet, and verify that the door is securely closed before attempting to start again.