Can't See or Purchase an Unlocked Azerite Essence

Most Azerite Essences are designed to be accessed in order of ascending rank. If you've unlocked Rank 2 of an Essence but cannot see or buy it on the appropriate vendor, you will first need to gain access to Rank 1.

Currently, the only exceptions to this rule are Essences obtained from Island Expeditions, Mythic+ Dungeons, MOTHER, and Rated PvP.

Note that MOTHER will have the red error "Learn Rank 3 on another character to unlock this essence" on essences that are already known.