There are a few things that will keep the drum from tumbling, the belt being broken or slipping badly, the motor being seized, or worn support parts.
Dryers have a belt that turns the drum. If the belt is worn or broken, it can’t move the drum. Sometimes just replacing the belt doesn’t do it; ApplianceQuest will also check the idler pulley. Wear on the idler pulley can cause the belt to break.