OpenRA

I was playing a single player C&C game on the East vs West 3 map and couldn't figure out how the Viceroids work. I captured the Biology Lab with an engineer, then the Viceroid popped up on the infantry tab. I tried building one, but it was grayed out and said I needed a Biology Lab.

I've only played OpenRA twice now, but Is this a bug? Or am I doing something wrong?

Thanks for the game, it really brings back memories!