[ChuckS]

Looking at your monitor panel .. display commander (DC) looks like you have the JRVCS2 Gen 2 In Command system

I’d suspect the BCM is receiving a fault indication from the water heater ignitor module board when trying to run in propane mode...

The BCM on your system receives the fault signal ( failed to light ) for propane mode only...there...as far as I can tell is NO fault indicator sent if your water heater isn’t working in 120 volt AC mode using the heating element..

Looks like you have the Suburban SW12DEL series water heater and schematic for the suburban shows no fault light for electric mode....

Pics show where on BCM the signal is sent to from the water heater igniter control module to the in command BCM..

I’d remove the water heater ignitor/flame sensor and clean it and set gap at 1/8 inch and reinstall and see if water heater is actually igniting in propane mode

See pics for BCM pin out for water heater fault signal from water heater ignitor module

Last two pics show where to remove bolt to slide out the ignitor/flame sensor and gap measurement