This entire quest has been bugged for over two months. Numerous people have already mentioned this concern:
https://discussions.ubisoft.com/topic/91320/can-t-progress-lost-glory?_=1610741887366
https://discussions.ubisoft.com/topic/92141/lost-glory-quest?_=1610741887368
https://discussions.ubisoft.com/topic/83905/lost-glory?_=1610741887364

However, the issue is not mentioned in the known issues thread and it was not patched in 1.1.1

The bug occurs when a player accidently talks to Halfdan before starting the "Lost Glory" quest (for some reason he is already spawned with a dialogue box before the mission begins). Not being able to complete this quest then keeps players from finishing the Order. Also, I have tried reloading the game from the title screen, desktop, and fast traveling away and back. Do you already know about this issue? If not please start working towards a fix, it sucks to get this far and not be able to complete the game.