That can also happen with the vanilla AI. It usually means that the AI's fort has become so badly morphed that the game can't track what to rebuild, or that the terrain of the map was changed so the AI can't place nodes properly.

Did you attack it first, or does it stop working at the start of the game? Are you playing it on a custom (Workshop) map?

same problem. At first they play pretty well, but when they reach a certain point they just stop developing. They sit and do nothing. Even if you haven't done anything to them yet.