Bumping this in hopes of a blue response. It’s really irritating.
trying to get in myself not working, nothing is working as intended and they need to look into this.. ive read your alts are supposed to get this item that lets you skip all the quests but none of them do.. then i read what quest i need to even begin heading inside but apparently that doesnt exist either so wth
Went mad trying to figure this out myself. Scoured forum posts, wowhead articles, discords, etc. After banging my head against a wall, eventually, I figured it out. Check your main, whichever you did the quests to reach the dream on’s achievements list. If you don’t have the Defenders of the Dream achievement on them, you’re not done. Finish the whole emerald dream storyline, then you should be offered the quest Fair Skies and Strong Winds by Alexstraza. Complete that, as well as the following quest Siblings Until the End, and the portal in Verdrakken should finally appear for all characters. Did this on my horde character, and it’s there on my alliance alt who has never touched dragonflight. Hope this helps someone else tearing their hair out over this.
Has this STILL not been fixed? Aboslutely freaking ridiculous.
I’ve done the entire questline, including gaining the Defenders of the Dream achievement on my main, and still cannot enter the dream in valdrakken or the ancient bough with my druid alt. 
Are the two characters on the same server? I found that when I got onto an alt on a different server the portal was absent aswell. If they are on the same server, I have no clue.
Same issue, my main can access the emerald dream without problem but my alt can’t..