I recieved the quest to recover Pantea Ateia's Flute.
I already had the item in my inventory after finding it in a dungeon earlier.
After accepting the quest, I can no longer initiate dialogue with the NPC and turn it in.

I've attempted to leave the building and come back, as well as waiting for a few days.
Neither of these fixed the issue.

Hey, just had problem myself, checkout the link below. It's shows the bug list for this mission and how to resolve using console commands.

Cheers,
Jaeger.

Hopefully it'll be fixed at some point....maybe.

But for now, here's the solution I used.

setstage bardscollegeflute 40 (Quest movesd to the 'Flute Found' stage)

That will allow you to complete the quest.

Of course, it's then stuck in your inventory. So use the following command.

Player.removeitem 000DABA7 1

And for the other two items for the Bards College which also remain in your inventory, though the quests themselves aren't bugged.

Player.removeitem 000DABAB 1 ( For the Lute)
Player.removeitem 000DABA9 1 (The drum)