Very weird. I tested my mission I am working on. Artillery doesn't fire, even after 15 Minutes. When I assign a target point and click "start", there is a countdown on the left side, approx. 160 seconds, it says "aiming". after that, there is "aiming" again, and a negative number, -300 counting even more negative (-301, -302, ..) forever. No firing.
DCS closed, new mission, only 1 artillery, Tactical Commander slot...everything works. Tested around a bit, didn't know what I have done, but suddenly the artillery showed the same behaviour as in my mission (not firing, weird aiming-countdown).
DCS closed, another brand new mission. Placed 1 arty, tac com slot, ordered to fire...and..nothing. Weird aiming-countdown, no firing.
Restarted DCS, new mission, artillery firing normal. I was able to see between the "aiming" and "launch"countdown there is a short switch to that negative countdown.
New mission: normal
New mission again: normal
New mission again, added MIST at mission start: normal firing.
My mission: not firing, negative countdown