Hey!

I've been having an issue with Serana's and the death hound's dialogue boxes. Whenever I press E, their dialogue box won't appear. Serana simply turns to me and says yes, but nothing else happens. The death hounds just look at me and continue their patroll. Even Lord Harkon's dialogue box(after giving me the vampire lord gift and a speech on how to use my new powers) sometimes glitches. However, his box appear, it's just that the text is un-clickable.

I got the legendary edition with every expansion+ there's no mod installed. Also, Serana's dialogue box works perfectly until I've reached the castle and turned into a vampire. That's when the problems start. I've tried to reload a previous save file and reinstall skyrim but nothing seem to work.

Any ideas on how to fix this?

I know you said no mods, but have you tried the Unofficial Patches?

You will still have to load a save from before this glitch occurs, but try the UOPs, there is an active thread in the mods section, usually in the first two pages.