Water Heater Wont Fire On Gas

I have a 2002 5er with a 10 gal atwood water heater. It works fine on ac, but about a year ago stopped working on gas. Everything else in the trailer works fine on gas, fridge and stove. It sparks fine and tries to light, but goes into lockout mode after 3 attempts. I have replaced the thermostat and eco, there is voltage at the solenoid and I hear that distinctive click when the heater is turned on. I also replaced the board today with another known good one, but it did the same thing, 3 attempts and lockout, which I tried multiple times. I cleaned all grounds and used those grounds to check voltage at the solenoid, and they worked. I also cleaned the nozzle in alcohol, still no go. Any ideas?