Forgotten Drangi of Ragnar (Assassin's Creed: Valhalla)

The game was played a long time ago, while waiting for the update, sometimes I go through side tasks.
All drangs are killed, went to the location for a dagger, next to Jorvik. The cell is there, the green task symbol on it glows. The serpent killed. And that's all. The triangle does not appear, the dagger does not fall out. Even the video cannot be activated to view Ragnar's story.
What am I doing wrong?))
Thank you!
Search smoked, except for the description of the quest - I could not find a solution to the problem. Maybe he smoked badly (.