There usually two limit switches located at either end of you burners. The have a football shaped metal mount with a black round plastic assembly on it with a red or blue button in the center and has two wires connected to it and run from one to the other on one side. Locate these limits and push in the button to reset them. They will click slightly when reset. If one or both reset retry the call for heat and at a safe distance try and observe the lighting sequence and see if it starts. Let me know if this helps. If not i will need the make and model # XXXXX your unit.