So I’ve done the quest which opens up the portal from Boralus TO Silithus on my freshly dinged 50, but am not able to take the portal FROM Silithus back to Boralus again. Nothing obvious in-game to explain this inconsistency, what’s the issue?
This is on a freshly dinged alt (Zlic-Silvermoon)
In case anyone comes across this, the portal appears to require the ‘Come Sail Away’ achievement, at which point it will appear.
The Horde equivalent would be the ‘Welcome to Zandalar’ achievment.
I’ve done that… I still don’t have it 
got to Nazjatar, completed there… got the legendary cloak… still nothing.
Suggestions please? 
Have you done the sanctum of the sages quest?