So I recently did my started the dawngaurd dlc and I wanted to cure my seeks off werewolf (despite the Vampire Lord removing it) or didn't work so I stated the purify quest for vilkas and it told me my follower left me services I walked out Serena came out with vilkas and he walked back inside I talked to him he said looking for work I said yes had to rescue someone now im art the point were I need to funny thw mouth priest I want to bring Serena but she says I have some one but i don't the people I rescued are home Serena was my only follower and nobody will join me i cane load back and I can't remember witch quests force me a follower and I can't load back to previous save.
And I didn't ask any body to follow me i waited days(enough days to become blood starved) and i reloaded help would be appreciated if nothing works ill do more of the Dragon born questline until that skall lady joins me(hopefully by force).
Best Answer
As soon as you complete your "Moth Priest" Quest Serena will start to Follow you again
I was once in the same scenario and just simply did the mission and after that Serena will start taking orders again.
if this doesn't help let me know and i will try to reply quickly