Fallout New Vegas:Need help completing the mission For the republic part two when dealing with the brotherhood?

I need help i am on the mission "For the republic part 2" and i neeed to destroy the bunker. The thing is i have already made Hardin the leader and i have already complete veronicas quest, but when i talk to hardin it wont give me the dialouge to make the brotherhood join the ncr. Since Hardin is leader i can no longer activate the self-destruct termimal because i cant get all three keys. (Glitch ?)