Several different problems could prevent your dryer from heating. You could have a failed heating element, a wiring problem in the heater circuit, a failed operating thermostat, an open high limit thermostat, a blown thermal cut-off fuse, a failed timer contact or a bad motor centrifugal switch. A voltage problem would also prevent the dryer from heating.
I recommend checking the breakers for your dryer first. The dryer will run if only one of the 120 volt legs of 240 volt power is supplied to the dryer. If the second leg of 120 volt power is missing, then the dryer will not heat.
If the breakers are okay, then I recommend checking the voltage at the outlet using the diagram in the first image below. NOTE: You should only check this live outlet voltage if you are completely confident in your technical ability to safely measure it using a volt/ohm meter.
If the outlet voltage is okay, then I recommend
unplugging the dryer
and removing the back panel. Check the wiring between the components shown in the second image below. Check the heating element to see if it has any broken coils. If you have a volt/ohm meter, you can check the resistance of the element. Remove one or both wires and measure the resistance across the leads of the element. You should measure between 7 and 12 ohms of resistance. If you measure infinite ohms (open), then the element is broken and will need to be replaced.
If the heating element is okay, then you can check the resistance of the operating thermostat, thermal cut-off and high limit thermostat in a similar manner. These components should measure near zero ohms of resistance. If a component measures infinite resistance, then it has failed and will need to be replaced.
If all of these components are okay, you could have a wiring failure, a bad timer or a failed motor centrifugal switch.
These tips should help you determine the cause of your dryer heating failure. If you need more help, resubmit your question with additional details.