THIS COULD BE MY ANSWER: check the ignighter,that is what was wrong with mine took 20 mininutes to fix,called the repair shop and they told me that this is the most common cause $30.00 for the part.can get to the parts by removing the front of the dryer. hope this helps,for a quick check for the ignighter remove the front of the dryer disconect the gas supply first and plug the dryer in to power suppply turn on the dryer and watch the ignighter if it glows after a few seconds then it is somthing else if it doesn't glow than i would change it,only handle the ignighter by the ceramic white part | 
No heat for gas dryer, fine other thatn that 
