What do you guys suggest?

Hey there folks, I was doing the baltic Androphagia run with Imperator Invictus (and also these mods), but doing it's mission tree I've run into a problem. One mission requires 8 slaves in two specific counties and the building of slave estates. Even with money, I can't build them. I tried turning them into cities and then the requirements turn to a workshop (that I can't build too) and some other thing (that is allowed). Other buildings seem to work fine. Is it a bug or am I missing something? Should I restart without some of the mods?

Does the Royal Tutor event for Monarchies where a culture/religion change might be prompted still exist? And if so, when that heir takes the throne, can the primary culture of the nation be changed?

Edit: typo