Although I finished the Thousand Eyes quest (shows up in Completed Quests log), can do daily contracts and have full access to Reda's shop, the Thousand Eyes Core Challenge refuses to pop. It's hardly a game breaker, but it bugs my completionist OCD being stuck at 34/35 Core Challenges! 😞
N.B. I have completed the base game, side quests, mysteries/armour/books, all regions (incl. Asgard & Jotunheim), River Raids (full St. George Armour set), the Druids DLC and all but 4 Achievements.