So it is spark to pilot flame then? The ignition assembly 1/2 way back on the burner. Most of the units up here have been "hot surface ignition " for a long time to meet efficiency and code requirements, so never thought of spark. If the flashing code says clear then as far as I recall from doing residential work years back, that is is most likely not proving air flow.
Some Carrier models you could disconnect the thermostat then jumper across 2 pins on the board marked "Test" and it would run it through the pre-firing sequence
You do check your flashing code before you turn power off and before you open the cabinet door? The cabinet door had a switch that killed power on some models before you could read the code. We drilled a hole in the door so you could read code first.
Residential work was 15 years back now, I can tell you easily how to get a 35,000,000 BTU high pressure steam boiler fired if you need.