Hello: You must have a power vent heater. With their added controls and other electrical equipment, they are more akin to commercial heaters than conventional residential heaters. There is more to go wrong and it is likely your heater’s manufacturer has put together a troubleshooting flow chart. This will help you (or a technician) to diagnose and pinpoint the trouble. So, your next step should be a call to the maker (or perhaps visit their web site) to get the needed information. Sadly, there are lots of ways for simple heaters to misbehave and even more ways for complex heaters.