Blizzard has announced that they are looking into issues with Nightmare Dungeon rewards for three dungeons: Akhan's Grasp, Buried Halls, and Edless Gates.
Hello all -The team is investigating an issue and working on a fix with rewards not appearing for players who complete the Nightmare Dungeon for Akhan’s Grasp.The team will be rolling out a hotfix for this issue in the near future.We are also aware the normal Dungeons for Buried Halls and Endless Gates are not awarding rewards upon completion and are looking into a fix for that.Thank you for the reports on this.. Read more on wowhead.com