Destroyer Cannon Help

[Danok_Delta]

Trying to get a Destroyer Cannon kill for the season pass stuff but I can't get the gun to shoot.
I assign a crew to it but they never fire and when I try to rotate the gun the crew starts to rotate then stops.
I have tried the cannons in the skirmish map as well as in the Saxony challenge map, same results.
Does anyone else have this issue?

[Atramint]

They can be a bit finicky with aiming. Sometimes I will rapidly right click in a spot until their firing arc moves to it, it seems to help. Otherwise you can try to lure an enemy in front of it.