I play on PC and the ascendant challenge is broken. I have completed it several times, playing solo. After killing the boss it fails to complete. No gear drops, no chest appears, and no portal opens, and the bounty does not complete. I remain stuck there. The only thing that does happen is that the bombs switch over to taken cannons, or vice versa. EDIT - It eventually worked after running the challenge with a friend. Still took two tries that way.