I'm playing the full April 1861 campaign as the CSA, it's early October 1861 and I noticed a number of artillery units are in the red, so I go to the replacement screen and there is no artillery displayed so I can't buy replacement chits (I can for other types besides artillery). 1st attachment has the screenshot, 2nd is the game file. I tried clicking on the arrows in the replacement area of the screen to see if it would scroll and display more unit types, but no luck.
I checked another game I recently played as USA, using the same campaign, and the artillery replacements are displayed on this screen.