Unless I'm forgetting something, I'm sure something went wrong with my Dawnguard quests. I took Serana to Volkihar and was given the quest 'Bloodline'. I refused the gift and was banished, finishing the quest. However, I'm getting nothing telling me to go to Isran, and when I do talk to him I get no dialogue options to trigger the next quest.

Has something gone wrong? And if so is there a fix? I'm on Xbox. I did load a previous save from waaay before I finished the quest, and that didn't solve anything.