So I recruited Sorene and Gunmar, went back to Ft DG, Isran asked me up to have a chat with Serana, and she isn't even there. Tried waiting. Dunno what's up with this... I had a mod that allowed me to join the DG as a vamp. Tried disabling it but that didn't work. I don't have any other mods that alter, Dawnguard, vampires or really anything DG related, so I don't know what could be causing this.

Any help?

Fixed it. Just started the quest using the console, hope that didn't screw anything up down the road.

The question is has Serana come back. She is important through out the MQ. If she is no where to be found it might be worth going back to a previous save to make sure she didn't skip out of Skyrim on you.