Just had a look at it.
Looks clean to me.
Its a small map and cannons can shoot that far, just not with grapeshot. You need to use the 'attack ground' button, the range is quite far that way.
See picture below, you need to click on (1) untill you see (2) and then right click on the ground ( between the troops) where you want to attack.
Also, look on the minimap, i'v have selected one off his cannons, look where the X is located, its right in your troops where he is shooting, thats where he put his attack ground attack icon(2).
Don't select your cannons and rightclick on the enemy because they will move closer and use grapeshot, by the time they get close enough at the enemy they are captured.
Try this out in the editor, you will see.
Btw, if there is water on the map, and fishboats are allowed, use the scatter out selection, by selecting your army AND the fishboats by drawing a box over the map , then move your troops out, they will scatter out and be less vulnerable to these artillery attacks, BUT beware off charges against you.