either the heater element is blown or your heater control system is the problem.
The heat control is usually a simple affair with ceramic bimetal snap switches ( thermostats )
Unplug the dryer and remove the back cover and check.
If you have ever been guilty of turning the machine off before the cycle has finished by itself? Then almost certainly you will need a complete Heater Unit fitting. 🙁
There are 2 variants for this model (early & late production types) so in order to establish the correct part we would need the full Product number (12 or more digits beginning with 3??????????? 😉