Hello. Any help would be beneficial. My clothes dryer will not power up when the "start" knob/button is actuated/turned on. The unit is plugged in. The circuit breaker controlling it is not tripped. The door closes completely. I suspect the start knob is defective, but it could be anything other than that, too, I assume. Any ideas?

A bad thermal fusr at the back of the vent housing will cause this problem. They are non resetable and need to be replaced if bad. You can jumper around to test or check with ohm meter. A bad door switch will cause same problem