There is some problem with the homebuilt "GEN3.6 to 55 pin adapter harness". Maybe sectrig polarity is not inverted, or signal level is lower than signal threshold (measure sectrig DC voltage). For sectrig, LM1815 is usually set up with LM1815pin5=5V and 1k pulldown to GND (but weak 10-18k pullup can also work if signal levels verified carefully with scope). You might see more from triggerlog (eg. if only have primtrig, and sectrig is missing).

Marcell