So I have Dawnguard completed, and still have the Dragon Elder Scroll in my inventory. Well, when I get the quest to go talk to Paarthunax up at the throat of the world, he tells me I need the Elder Scroll. Well, it doesn't register that I already have it and I'm thinking its because it isn't coded correctly since I got it already for the Dawnguard questline, and now I need it for the main questline for vanilla skyrim. Also, the quest Elder Knowledge doesn't even activate, which it is supposed to once he tells me to go find the Elder Scroll. Can anyone help me. I am on xbox one, so console commands are out of the question.

Do you have a close previous save?

I find that sometimes happen on PC when I rush the last dialogue before a quest-check. Just reloading the closest auto-save and talking again, and letting the NPC finish the last sentence without clicking anything, usually solves it.

Couldn′t really help you if it′s anything more specific, sorry.

The only other thing I can think of... if you don't have a close save to revert to... Is to go sell the scroll to Urag at the CoW and then buy it back.. make sure you have the 4k gold to do so...he gives you 2k for it. then return to Paarth... try not to FT to him though.. I've read over the year's of people having issues when they did.. some never do, but why take the chance?

Buying it back from Urag will make sure the proper ID is on it.

edit: TES advice...save and save often!