@alexia_8
I'm having exact same problem. I'm playing on PC with latest patch as of 2/4/2021 (1.1.1?)
I never picked up the brooch before. I didn't enter the castle before this quest.
When I enter the basement where the brooch is found and what looks like the dead Ealdorman, with the woman taking care of the body, I get no cut-scene. Nothing. If I pick up the brooch, I get a voice-over from Eivor that "this should be enough." But the quest marker does not update back to the son who's waiting in Lincoln.
I'm stuck and cannot progress.

There is another, longer thread on this bug on Reddit as well. It seems like many people have this problem.

Thanks Ubisoft for getting this game breaking bug fixed soon.

@alexia_8
I'm having exact same problem. I'm playing on PC with latest patch as of 2/4/2021 (1.1.1?)
I never picked up the brooch before. I didn't enter the castle before this quest.
When I enter the basement where the brooch is found and what looks like the dead Ealdorman, with the woman taking care of the body, I get no cut-scene. Nothing. If I pick up the brooch, I get a voice-over from Eivor that "this should be enough." But the quest marker does not update back to the son who's waiting in Lincoln.
I'm stuck and cannot progress.

There is another, longer thread on this bug on Reddit as well. It seems like many people have this problem.

Thanks Ubisoft for getting this game breaking bug fixed soon.