Diagnosis
The drive motor is trying to run but can't. This is a seized idler pulley, broken drive belt, or a locked-up motor.
How to Fix It
Unplug dryer. Remove the front panel. Check the belt. If it's intact, manually spin the idler pulley. It should spin freely. If it's stuck, replace the idler pulley assembly (part # 310367). A seized pulley will burn out the motor quickly.
If That Didn't Work
The motor itself may be jammed. Try turning the drum blower wheel by hand at the rear. If it won't budge, the motor bearings have failed. Replace the entire motor assembly.
Heads Up
That humming is the motor overheating. Don't let it try to run for more than a few seconds. You'll burn out the windings.