I opened a ticket, but I figured I should post here too.
I leveled my new Zandalari Troll character to 110 and did The Stormwind Extraction, where you sneak into Stormwind. When you finish the scenario you end up at the Port of Zandalar where you’re supposed to hand in the quest. But the quest NPC is not there, so I can’t finish the quest, and therefore cannot begin leveling through Zandalar.
Anyone else experiencing this bug?
Yes, I was experiencing this bug also. To fix it (after several failed attempts to abandon the quest, relog, etc.), I abandoned the quest, relogged, and went back to Orgrimmar. I re-obtained the quest and VERY quickly clicked on the “skip” option from Nathanos (I only had a second or so to click on it, but if you abandon the quest again you can re-try as many times as needed). That ported me to Zuldazar with the quest flagged as “Ready for Turn-in,” and the NPCs were there for me. I hope this helps!!
A couple important notes: don’t click on the portal next to Nathanos if you get the quest again from him, since the NPCs you need to turn the quest into will not be there/will not have the question mark icon over their head/s. Also, you will miss the quest to meet Rastakhan by doing this, but you’ll still get the gold/xp from the original quest.
Confirmed that this works. I was getting irritated after going back and forth five times and finally found this.
I’m experiencing this bug atm and nothing is workingggg 
Normally I do not post on old issues, but I can confirm that this is ‘still’ occurring.
This bug is STILL occuring, fix your crap blizzard!!!
Another month and a half has passed and still seeing this bug. Very irritating.
I am in the same boat - got all the way to the final stage, and then all the NPCs disappeared. I had been careful to kill everything that stopped the friendly NPCs along the way.
Abandoned and attempted to use the “skip” dialog, since I confirmed I have a character who has already run through the scenario, but no skip dialog was present. I will have to try again and see if it shows up for a second if I’m quick.
EDIT: No luck with that, even with a completely fresh Interface/WTF/Cache.
This is still happening. I had the option to skip it, still happened. Went and abandoned the quest and actually did the scenario, same thing happened. Opened a ticket, but why is this even still happening?
So I’ve been getting this on my Mage for about a year now. Would accept the quest, skip the scenario, be taken to the port but Talanji wasn’t selectable to finish the quest. Finally said screw it, flew up from the docks to the Great Seal just to see what there was to see and there was Nathanos at the war table ready for the turn in. Was able to turn it on and start the campaign. So not sure if that helps, but worked for me.
594 days since the original post was made and guess what…it’s still bugged during the pre-patch to the following expansion…
The quest turn in isn’t where the “Campaign ?” is. Nathaniel is up in the Rest Area, center of pyramid where portals are. It appears as a normal Question Mark.
How is this still bugged? Fix your dumb game.