Atwood furnace shuts down after first failed ignition

Ok, I was wrong about the t-stat. Jump starting it by directly connecting the t-stat lines also causes the board to shut down the fan on a failed ignition. No purge cycle, no power to the board.

I'm out of ideas. The relay is working perfectly, the board is new enough that unless it's a dud, it's not a consideration, the t-stat has been ruled out, the ignition gap is fine...