If you fight Chris, or argue with him or some crap, it'll break the quest. I'm not sure how to fix it. More than likely you'll have to do it on a new character. I don't think you should really bother, though, as BoS is currently broken and entering the faction will only give you access to their bunkers, which contains nothing useful as the Faction Point system (at least from what I've seen) hasn't been fully implemented yet.