Artillery will not fire

[Cicero]

Maybe I am just a greenhorn...but having artillery pieces that do not fire when I need them to is aggravating.
At any given time, either the cannons will fire (very rarely) or they will not fire even though my reload time is at 100% reload (and will stay that way for the duration of the fight) and regardless of what unit I order them to attack.
Elevation and LOS are sometimes the cause for the absence of firepower, but not always.
Same with range and reload time.
I have yet to understand why the cannons fire when they do and why they do not.
I end up constantly trying to salvage a fight only with the infantry and maybe cavalry, but the I suffer a lot of losses every time, especially since the AI has no trouble at pounding me with its artillery pieces.
For example, after the opening salvos of my artillery when I play Union at the very first battle of the campaign...from then on, I am lucky if the artillery fires even a single salvo (the artillery stays put and doesn't fire or at one point simply runs when the enemy is too close).
Not to forget the union artillery which becomes accessible near the end of the battle, but will not fire on targets within the maximum range of fire.
In the meantime the AI is blasting away with its cannons.
On all accounts, my artillery stays put at 100% reload time since its appearance, and maybe...just maybe the cannons will give me one salvo...if I am lucky I'm get a second salvo, but no more.
So, like I said, I find this aggravating.
Could someone please explain to me what am I doing wrong?

[Technopiper]

This post by the developer may answer some of your questions: https://steamcommunity.com/app/306660/discussions/0/35219681586567749/

I remember that in an earlier version, the artillery will move itself to get in line-of-sight of the target you assigned, often leading to suicides. Later versions removed that behavior.

[Casey]

The elevation and geography around Gettysburg greatly benefits Confederate artillery in the west, northwest portions of the map. This changes as/if the Confederates make a push east/south-east toward Cemetary Hill, wherein the Union will have a large field of fire with which to shoot their cannons. Bascially, it's just the terrain. If you're the Union and have a line on the west-side of Gettysburg, north, and north-east, you're going to have to find firing lanes for your cannon which will frequently make the cannons unable to fire. I agree it's a little aggravating because the elevation key does little to help demonstrate the elevation changes, what's "in the way", or any sense of obstruction.