Atwood Water Heater gas comes on-only electric switch is on

I flushed out my water heater today. Got a lot of the white flakes out of it. I put the plug back in, turned the water on, and then flipped the 110v water heater switch. However, when I did that, the gas came on and heated it up. The gas side was turned off. If I turn 110v off and turn the gas side on, the gas lights and it heats. If I turn the gas side off and turn only the electric on, the gas lights and it heats.

It was all working fine until today.

Any thoughts would be welcome.