Also, if you have your torp space with just sailors in them, and no guns/torps launcher, they will say

"Cannot fire even if you leave the port"

and yes, you may have forgotten to load up some ammo on a gun or two


Solution,

1) Ignore (I have nothing in my trop space, so i just ignore the voice)
2) Load up guns/torp launchers in your torp space
3) Load up ammo on all guns

if it is continually telling you that you have no ammo it means you are probably driving an atlanta with the rear guns unloaded when your in the shipyard there is a scroll arrow at the bottom right corner use it to see the last 1 or 2 guns and load them it will fix the voice in battle and improve your firepower by a bit

wont do anything about the voice when you leave shipyard though