Apparently it requires some quest from dragonflight which isn’t directly accessible. Where exactly does the quest series required to gain access to the Eye of Eternity begin? Quite a shock after coming back to the game after couple expansion break that you can’t reminisce by doing all the raids anymore.
Wait! What?? Who told you that?
No.
I do see some comments about being phased if you are on a quest from Battle for Azeroth, a Bolt from the Blue, where you have to meet Kalecgos there. And I remember it played a part in the Dragonwrath questline from Cata, somabe that would interfere as well.
So maybe, if you are on some questline where the RP requires you to show up there and meet someone, you have to get that out of the way first, before you can use the normal, un-phased entrance.
But no. Just no. A normal, healthy level 80 can just walk in.
So what is going wrong for you? Maybe we can figure out what is happening. Remember, the entry for The Eye of Eternity is the top portal in the Nexus building, above the portals to the Nexus and the Oculus.