Gas Dryer wont heat??
I, too, have little experience with gas dryers.
However, on an electric dryer there will be several heat settings; like delicates, regular and permanent press.
If you have the same or similar settings on your gas dryer, try running the dryer on the delicate cycle instead.
An electric dryer will have two different thermostats; a low temperature thermostat for the delicate cycle and a high temperature thermostat for the regular dry cycle. The Permanent Press setting uses the high temperature thermostat but shuts off heat to the dryer about 20 minutes before the dryer drum stops tumbling the clothes so that any heat-wet creases in pants or shirts or whatever don't come out. If the clothes are hot and are allowed to sit in a stationary the dryer drum for any length of time, any creases in the clothes will become "permanent pressed" too. By tumbingling the clothes until they cool down, the permanent press cycle prevents new creases from being set into the clothing.
Anyhow, I digress. Try running the dryer on the different heat settings. If the dryer works on all the "Delicates" heat setting, but not regular or Permanent Press, then it means that the High temperature thermostat is stuck open and you need to replace it. However, if the dryer doesn't heat on any heat setting, it's more likely that the thing that actually does the heating is shot. In an electric dryer, that would be the heating element. In a gas dryer, that would probably be the gas valve or ignitor.