Atwood water heater only heats with 120volt

Update for all. It works. I suppose it's operator error. I kept turning it on when water was already warm. I used meter and wiring diagram. Realized thermostat was open. Ran water until thermostat closed and it fired. I'll clean some connections to be sure but I think I just had head in clouds because vacation wasn't going well. Truck in shop for u joints :(. Anyways thanks.

Info deleted.........no response from OP

Can you hear it spark? Have you tried turning on your gas kitchen burner to insure air is purged from the line? Can you smell gas near the burner tube? If your sure the water heater is getting gas and it's sparking then you might try and remove the spark assembly (easy, one screw removal) clean the ends with emery cloth and make sure the two probes are within the correct distance of each other (easy to bend).