Atwood Water heater cold start problem on gas

I have a Atwood water heater that has a hard time starting when it is cold, hasn't been used for a day or so. It lights, burns for about 10 sec then the gas shuts off and it quits. It goes through this cycle about 5-6 times before it finally lights and keeps burning. I replaced the ingniter and that seem to help, but the problem is still there. Once it warms up it works fine. Is there some electronic brain that is not getting a signal that the burner is working?

Any ideas would be appreciated.

Thanks
Peter