Can't call arty in RV "Duel in the Ukraine"

[FroBodine]

I'm playing Red Victory's "Duel in the Ukraine" scenario as the Soviets. I am unable to call in artillery support.
During the 1st turn, I was able to click on the air/artillery command from the leader menu and see I had artillery support. But, I did not choose to call any at that time.

Now, I am unable to click on the air/artillery command and get to the artillery dialog during any turn. We're on turn 4 now, and every time I try to get to the arty dialog box, no matter what leader I select, I get a beep and it says no valid unit to call in artillery. I still have my radio guy.

Is this a bug, or what am I doing wrong?