I have a kenmore gas dryer approx 3 yrs old recently it quit working runs but does not heat I changed celonoid also thermostet/flame sensor help parts I used were from older model that I replaced in past

Did you check the parts you put it to verify they were good? Do you have flame? Gas dryers ar very senitive to having a clean vent to dry properly. Check lint trap and vent hose from unit al the way out to where it exits house. Many times birds etc will clutter up the hose where it exits house.