I've checked all the hints in this thread and one other thread about the cannon. Turn on "arms" power switch, switch on left panel forward, hit the "pyro" button to cock the gun.
No guns. The AoA light will not go out in level flight at +315 kmh. The gun camera will activate, but no shooty shooty.
Twice now, I've expended rockets on targets after deciding, "screw it then, I'll pass on guns", and after a couple of passes, the AoA light blinks out and the cannon starts working.
I've attached a track. This is driving me crazy. I want to come in with cannon first and enfilade the column. Then turn after they scatter and use the rockets to mop up. But I cannot get the cannon to operate before I use rockets. guns.trk