Suburban SW6P no spark

1993 6 gallon Suburban SW6P in our truck camper.

Worked fine when we bought the camper, then would light, burn for 5 seconds or so, then shut off. Able to get it to work again by blowing out burner tube (probably coincidental). Worked for five trips, now won't spark. If I turn it on, I can light it with a lighter, but again, it burns for 3 seconds, then shuts off.

-No visible spark when observed in the dark.
-Reset fuse on high temp switch not activated.
-Oven, furnace, refridgerator work fine.
-12.7v at battery.
-I tried to bypass hi-low thermostat, but no change (might not have done correctly.
-Current 12.7v when checking input-output wires from thermostat, when thermostat removed.
-I can here gas solenoid opening/closing, also can light manually.
-Tried to clean temp sensing rod/igniter without success.
-Significant corrosion at mounting point for igniter (bad ground?).

I ordered new board and hi-lo thermostat, waiting for items to arrive.

Any insight?

I'm guessing the temp sensing/flame sensing function is gone. Or could it be a thermostat shut off issue?