The most likely cause of the problem is a fault belt drive. Drum dryers use a belt drive system to spin the drum and if the belt falls off the track or the belt drive has failed, it will cause the drum to stop spinning.
The dryer drum is turned by a belt. If the drum is not turning, it probably has a broken or slipping belt. You can replace the belt by opening the back of the dryer.
It may just be a broken or stretched belt. Remove the cover and see if the belt is broken/loose. If so, replace it. Belts are available at most appliance dealers.
