So I'm guessing this is your first attempt. (The last light of the sky fades on an empty city that used to be gal civ modding.)
Try looking at the tech tree requirements and the improvement list and make sure everything point to the other so to speak. (A ball of dust blows across the empty street into some dark alley.)
Also, are you using TA or just the old expansion. If you want to mod its easier to have the tools packaged with TA.