Are you getting signal from coil 32 on the driver board? That looks to be the one that controls the motor according to my manual. it shows it's 20V which is the same as the flashers. Maybe you could jump one of the flasher outputs to the canon to see if it moves any. I don't know if that can/will cause any harm though to anything but they are the same voltage.
If it helps, it's P1 on the J7 connector that controls the motor. (should be brown) Being that this should send 20V out until the game sees either switch 62 or 63 go closed (I believe those are the cannon home and away switches) you "should" be able to put a meter on their to see what it registers.
Jumping pins was the only way I found the switch issue I had on my MET thus the suggestion. Yours sounds more like driver board then switch matrix though.