Related to my ticket number US104579602, in the game, no NPC showed up at Broken Isles Dalaran to give me the quest for the serial.
Call of the Illidari (https://www.wowhead.com/quest=39261/call-of-the-illidari). This is the first step of the DH and leads to getting both quests.
“To Fel and Back” and “Livin’ on the Ledge”
to activate the Order Hall and to get the Twinblades of the Deceiver.
Secondly, I’m not able to use my Dalaran Hearthstone (https://www.wowhead.com/spell=226914/forceitem-dalaran-hearhstone).
Not being able to use your Dal hearth means the game doesn’t think you have started Legion content properly yet, which is then also why your class rep hasn’t shown up in Dal.
I’m not sure how you got to Dal (there’s lots of ways these days) but the only way that opens Legion content is to take the quest from the command board “The Legion Returns” and follow the chain until you get to Dal. If you have done it before on another character then there is a big skip so it is super fast.
Thanks for the reply.
For my character, there is no 7.0 quest on the command board.
I tried everything, almost completing all the critical quests in Broken Isles and completed the quest until “A Gift From the Six”.
Usually, the NPC for activating the 7.0 order hall will show up once the character gets to Dalaran automatically, but for my DH character, there is no such npc show to give me quest.