Can't attune to Titan HM

I have the quest "In a Titan Spot" and when I click the crystal to attune I get a quest dialogue and can click complete. Text flashes on the screen saying Quest Complete and that The Navel (Hard) is a available. It's only that it's not. The quest is NOT completed and the Duty Finder is NOT updated. Can't progress the Primal fight any longer.

My inventory was full, that's why I couldn't complete the quest. You don't get an item, but still you need to have at least one slot free. There should really be an error message so you know what's wrong!

Yes that's true, i had the same problem and it worked after removing a item