I hope this helps someone else with this problem. I finally fixed the problem myself. I called Rheem and they gave me some trouble shooting tips. Check the vacuum switch - which was fine. If not vacuum switch, likely the controller.

I actually replaced the controller and the problem went away for a few days then came back.

After exhaustive troubleshooting, I found a slightly open male terminal on the lead from the 24V transformer that connects to the gas valve. I was getting 24 volts, but the valve was not working. I reduced the gap with a pair of needle nose pliers and the problem is fixed.

I reinstalled the original controller and found that it was actually faulty. It would provide 24 volts for about 1 second then go to zero. So - I had two issues.

Again - I hope this helps someone else.

Thanks for the update. We appreciate the input as it will help others in the future. Tom