I found Castle Volkihar before I began Dawnstar and talked to the gatekeeper. Now, while actually playing it I have come to an abrupt halt. I traveled to Serana's home, the castle, with her as she requested and can't get the gatekeeper to open the gate. I've tried re-loading, re-booting, fast travel away and back to different places, swimming and boating to and from the castle, waiting around the entrance trying to force dialog and still can't get the gate to open. I even tried the wood plate clipping trick and I didn't work.

I became frustrated so I began Dragonborn but I can't shake Serana. She follows my character and Lydia like a stalker. I ask her to wait or part ways to no avail. She does battle as our advocate when attacked so that's a plus but I still travel everywhere with her.

I'd appreciate any suggestions or ideas I haven't tried to get the gate to open and continue or get rid of Serana. Thanks.

Lydia and Serana? You player! Well, that is weird. I know you said you waited but have you tried waiting a full 24, 48, 72 hrs at the gate to Castle Volkihar? Also, did you try talking to all the folk at Dawnguard? That may be needed as well to advance the quest.