*potentially mild spoilers*
Ok no prob jsut want to make sure I get the exact sequence of events here since I truly believe that is what can cause this issue. (The same types of bug behavior apply to a few other quests in DAI)
So you had found some of the research materials but not all BEFORE you had met him, and then when you did you indicated that you had materials and he acknowledged and then asked for more? I just want to clarify because I had them all before I attempted to turn in so there was none of that sub-step for me in my memory to use.
And during this same conversation (without closing the dialogue), you also accepted the other quests he had and proceeded to finish them all, possibly collecting more research materials as you went ya?
Also, after killing the dragon were you able to recruit him as an agent?
And finally, how many saves do you have currently? Do you have any from before you did all this that you can use to perhaps redo this quest line as a test? I keep a few hundred saves myself because I don't trust this game lol.
I just loaded up my game to see what I had finished, and here is how my sequence went:
- Had collected all research materials before ever meeting Frederic (Frederic's Livelihood)
- Had collected all lure materials before ever meeting Frederic (How To Lure A Dragon)
- Once I had these all, I eventually went down to meet Frederic (At this point the quest Draconology should be complete since you find him)
- At this time, I could go through all the dialogue with him and obtain the quests from the first two steps (Although I did not choose the options to say 'Here is your research' and such, I just said 'Goodbye')
- At this point he had also started me on the quests to essentially assist with his Dragon research (Sharper White Claws for the dragon traps, Hunting Patterns for the Dragon Signs, and A Manuscript Of Some Authority for both finding the Tevinter Writing on dragon luring and then the followup War Table opertaion to get it deciphered)
- Once this war table operation was done, I went down to visit him and turned in this quest. Then said 'Goodbye'.
- I then reopened the dialogue with him, and chose 'I have your research'. Then said 'Goodbye'.
- I then reopened the dialogue with him, and chose 'I have your materials'. Then said 'Goodbye'.
- At this point I received the quest for The Abyssal High Dragon. I went and placed the lured, killed the dragon, and returned to Frederick.
- He was overjoyed, and immediately offered to join the Inquisition at which point a new agent was acquired.
- I had no quests remaining at this point.
So I just want to confirm things went down in a semi-similar fashion (And that at least all of these quests were completed, and perhaps your variation on this sequence of events which produced the bug).
If it went down anything like this, I would definitely reload a save from before you meet Frederick to obtain all these quests, because if you don't see that objective clear up after meeting him the first time then you should not proceed with the rest of the quest chain most likely. As I said though I think it has to do with the way things are completed since there is undoubtedly some bug here depending on the circumstances.
Thanks let me know and we'll see if we can trace it further.