I'm having problems getting the terrain AI to work in one of my maps I'm working on, all they are doing is mining minerals and not building anything.
uhm first off try to name the ai script u are using
Expansion Terrain Campaign Medium.
I also have a protoss base in the map, but it works well when I use the expansion protoss campaign medium script.
Usually these AI scripts have certain conditions that must be fulfilled for them to run properly. Try using a different script.
And make sure that the location you are running the script in is only above the main building (Command Center in your case).