Originally Posted by Rockytop
I have to shut the thermostat off to get it to turn on again.
That sounds to me like it's not staying lit. It will try to light 3 times and if the flame goes out after that, it locks out and won't come on again until you turn it off at the thermostat (or otherwise remove power). If you're outside next to the vent, you should be able to tell if it's burning or not.
Do you have a bug screen over that outside vent? The manufacturer says not to use them, and I have trouble keeping mine lit of I have one on.