If it's the motor buzzing/humming when the start button is pushed then it likely has a bad motor. Open the door and manually reach in and rotate the drum in the counter clockwise direction for a couple of complete revolutions and then shut the door and see if the dryer will start. If the dryer starts; this would indicate a bad motor and it will need to be replaced. If it does not start and continues to hum try this; Open the door and press and hold the door switch in. Rotate the drum counter clockwise and have some one press start while the drum is turning. If the dryer starts, replace the motor.