Well this is old but i can't enter the [censored] soul cairn and Serana won't follow me for some reason, the "follow me" option does not appears when i talk to her. Some people say a DLC cant be patched but i know they can think of something. I don't know, a DLC that overwrites the current DLC without losing progress. I was lvl 85 when i dissmised Serana and now i'm 100... i wanted to recruit her when i was at 95. I have to much to lose if i reload the saved game when everthing was normal.

(I found a way to have Serana back but as soon as i dismiss her she won't follow again... it's a glitch to... temporary fix the glitch?)

...And i lost the chance to make Serana human again but it does not matter, from time to time i like to become vampire.

HALP MEH!!!!

"I found a way to have Serana back but as soon as i dismiss her she won't follow again..."

Why you have dismissed her again... (only curious !!!) (You could do a wait...)

Does it matter? i was triying to see if i could recruit her again but nop... i have to go to the undercroft in the Volkihar castle; wander around, i even killed those dead dogs; i exited, fast traveled and out of nowhere she appeared. And i do not know for sure if this works every time since i only did it once, it's a pain in the you-know-where to do all that just to get her back. I'm more of a loner when playing but some times i recruit especific followers for specifics missions. Makes me feel like i'm in charge, lol.

Did you go to the Soul Cairn as a vampire? If so did you become human afterwards?

The Cairn is finicky. If you enter as a vampire and get cured after that quest then you must have Serana turn you back (have her bite you on the balcony outside of Valerica's lab). After that you should be able to go in. If you went in human then I'm clueless.

As for the follower thing...I don't know as I've never dealt with the glitch.