I know why you're here. You're here because you race changed to Kul Tiran and you were expecting to be able to get this quest the way that every other Allied Race can do when you race change to them. Instead, you're greeted to the fact that the Harbormaster's Office is phased different once you are beyond level 20; Katherine isn't there, and there's no quest available. Worry not, you can simply make a new Kul Tiran and unlock the tabard's appearance that way.
Wait, what's that? You're not interested in the appearance, you want the quest and the tabard itself? As though they somehow complete your race change and make it official? Or maybe you're just OCD like crazy.
Well, me too. Unfortunately, it is phased in such a way that you can't see Katherine. Now, enterprising individuals like yourself won't let that stop you. No, you'll notice that beautiful word up there, "sharable" and you'll either conscript a friend or random stranger to share the quest to you. Success! You've got the quest. Only one problem, the first stage of the quest requires you to use the portal to Stormwind. "No problem," you think, you know where the portal is. Then you realize, to your horror, this particular portal to Stormwind doesn't count. You need the level 20 one that you can no longer see that takes you directly to the embassy. Without that, you're locked on that stage and can never complete the quest.
As far as I could tell, the only way forward from that point is CS, who (if you're lucky) will help you along and move you to the final phase of the quest. Best of luck!