Bari Mission 4 hard

Hi all, for some reason I'm trying to beat the Bari mission 4 (hard) and I cannot seem to make Cannon Galleons at all. I've researched chemistry, and it's still greyed out. I'm at a loss, did they remove making it from the scenario? or am I missing something?

Also this level is bonkers insane and I can't find a way through easily. Red pumps too many units that are seemingly impossible to fend off, and green's crossbows pick off people with perfect precision. Probably beating a dead horse here, as there's been other posts on this mission, but I'm having more difficulty with it now that I've ever had in HD.