Your thermostat is most likely bad. The low temp is closed but won't reopen at temperature. The high limit switch then opens and will need to be reset before the gas will be allowed to flow again.
Replace your gas side thermostat.
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Lou & Freya the wonder dog
2008 GMC Sierra 3000HD Allison Duramax
2019 Flagstaff 8529FL
Adjusting the igniter gap seemed to have fixed the problem. I haven't had to reset the WH since I adjusted it. Thanks everyone for your help and advice.