First of all check if you are getting 240VAC to the dryer.
Then with dryer unplugged check the continuity of the thermal cut-off and the hi-limit thermostats above the heater contacts.(Take one wire off when testing).
The thermal cut-off kit Part number: 279816
Another test is to jump the timer's contacts BK and R. If the heater comes on - replace the timer Part number: W10185972
Post the results.