Ok, so Ive re downloaded the DLC 5 times from Steam. Ive cleared the cache, Ive tried every imaginable solution to the situation. Yes my New Vegas is up to date. Nothing Works. Ive run through the initial mission for Dead Money 9 times, every single outcome is the same. Current save is one where I do not have a single person following me. They are all at the fountain. But the game still doesnt register them being at the fountain, so I cannot progress any farther in the DLC and I cannot leave.

This is an ongoing issue with a lot of Fallout DLC's that I have noticed. I have all of the DLCs for Fallout 3 and there are some of the Quests that are unable to be completed because what is supposed to be there is not, or somehow the person i am supposed to meet at a location gets killed instead. Case in Point, before I even had to a chance to talk to Ron from Girdershade, he insta died right in front of me with no enemies in sight and had full health and no explanation. I had it happen 5 times in a row.

At this point, i doubt i will continue paying for bethesda games if this is going to be an ongoing issue. And I have been playing the Fallout series since the very beginning.

Not too sure if i remember right but once you get all three to the fountain you then have to talk to the hologram again, have you tried that? not too sure if what happens next is triggered by a script that detects when all three are present.

Also if you are using any mods, disable them and try again.

(sorry if this is a bit of a silly suggestion but it's been ages since I did dead money and I didn't run into this problem)

Hope this helps.