Problem:
So you want to play the Dawnguard expansion pack and go to Dayspring canyon to join the Dawnguard. Unfortunately, everyone you meet starts attacking you on sight and there is no obvious way to calm them down.You look online to find why this might be and people suggest not being a vampire, reloading to an earlier save, or paying off your bounties. Unfortunately, you're good on all counts, but they keep trying to kill you anyway.
Solution:
Earlier in the game, you probably accidentally killed a member of the Dawnguard and angered the entire faction. I personally didn't remember meeting Durak, so maybe I killed him. To test this, I typed into the console:help durak 4
This told me information about Durak, including that his ID was 0201541D. So then I typed:
player.placeatme 0201541D 1
This spawned a copy of Durak in front of me, who promptly attacked me, which answers a few questions. Apparently I angered the whole faction.
So now I opened the console again and clicked on Durak so his ID was at the top of the screen (different than 0201541D) and typed:
getrelationshiprank player
This provided a value of 0 which means acquaintance. He shouldn't be attacking me, so it must be something about the faction. So then I typed (with his ID still active at the top of the screen):
setrelationshiprank <newdurakid> 3
This sets his relationship to ally. His ID is tricky because it is different than the initial number of 0201541D, but is easy to find once you click on him inside the console. You can verify his rank by typing:
getrelationshiprank player
But you shut down the console and he's still attacking! That's fine, it seems that when in this sequence he doesn't stop attacking until reset. So run off into the woods and hide for 24-48 hours until he's cooled down. When you return to him, he should be friendly. Then if you go into Dayspring Canyon, the Dawnguard in there should be friendly too.
Musings:
This is a ridiculous bug. I don't think that I have ever had NPCs attack me for no reason in Skyrim, especially supposedly friendly ones! I wish the game made faction status/NPC disposition a little more transparent and easier to modify because if you weren't on the PC, you would have no way to resolve this and would have no idea why they hated you. Maybe a calm spell would do it, but I don't know if it would work that well. This definitely deserves a patch because even if you do screw up and anger the Dawnguard, there should be a way to reset that or pay a fine to make them happy.In a real world sense, this might remove any playability from a $20 expansion pack. And in game terms, I'm the Dragonborn who has saved the world, I've killed untold vampires, head of the fighters/mages/thieves guilds. What more do these NPCs need? I'm am hands down the most famous and powerful person in Skyrim who is trying to join their cause...and they're trying to kill me? I know AI isn't the strong point of Elder Scrolls games, but you'd think they could fix this issue pretty easily.