I tried everything, I armed the 3 rows of switches, moved the selector switch to the V gun position, made sure the armament panel master arm is on, weapon safe is unsafed and red, and pylon selector on 624 (for the 12.7mm) or 622. I even pressed the push button on the armament panel to light up the trigger lights up top, but can't fire the guns. Got them to work in the training mission doing the exact same thing, but not in the campaign.