Advisor Vandros Didn't Drop the Eon Winder for Quest Rite of the Captain

The quest Rite of the Captain can only be completed in Mythic difficulty, not in Heroic and not in a Keystone attempt. You won't receive the Eon Winder if you have already killed Advisor Vandros in Mythic difficulty this week but before starting the quest. Do not abandon the quest: wait until the weekly reset and kill Vandros again.