A dryer that tumbles but does not heat can be caused by restricted airflow, a failed heating element, thermal fuse issues, or a control problem.
Dryers need airflow as much as heat. When lint builds up in the vent, the dryer may overheat internally and shut down safety components. If clothes take more than one full cycle to dry, it is worth checking airflow before replacing parts.
Tell us the appliance brand, model number, and what happened before the problem started.