I have completed all requirements to unlock Highmountain Tauren, yet they are still locked.
I am exalted with the Highmountain Tribe.
I have completed the achievement “Ain’t No Mountain High Enough.”
I have a 120 horde.
There is no quest available from the Orgrimmar Embassy.
There are no quests available in Thunder Totem.
The Highmountain banner inside the Embassy hut is green/unlocked.
The Highmountain Tauren creation screen is all red, even the things I have unlocked and that are green in game.
I have force quit the game, cleared cache, restarted my computer, etc.
You are not currently on any other quest to unlock a different allied race? I think you can only be on one at a time. Either that, or you already started the quest line for the Highmountain, but are somewhere in the quest chain.
If I had started the quest line and then abandoned it, where would the quest chain be? I have no quests at the embassy , Thunder Totem, or even the entire Highmountain zone.