Hi.

First of all check if there is 240VAC at the dryer's disconnect block at the back, be careful if you don't feel comfortable to work with "hot" appliance just try to reset the circuit breaker.

With unit unplugged:

Next, check the door switch for continuity between two contacts with wires on them (remove one wire off when checking).
You should read continuity with door closed and infinity with door open.
The switch Part number: 53-0148