There should be quests involving thrall bringing you up to the maelstrom and deepholm. Here is the quest chain: see if you can follow it and piece together a possibility you missed something?
https://www.wowhead.com/quest=39746/a-ring-unbroken#comments
Also check the comments, one of them mentions the shaman class hall questchain might be bugged and they link to this thread: https://us.forums.blizzard.com/en/wow/t/cant-get-shaman-class-hall-start-questdalaran-hearthstone/406148
It seems like you might need to do the legion intro quest first, have you done that already?