Ok, I have just spent all evening trying to find a fix for this with my very clever friend, and we just got a workaround. I ended up dropping everything from the catchup and went to the library area in Stormwind Castle (not sure what the equivalent is for the horde) and there is a scroll there, something about a message from Khadgar that has a quest. You might need to enable low level quests to be able to see it. Pick that up and it will take you to Dalaran to start the precursor quest where you run around with Aleria, and will eventually lead into the defence of Dalaran and teleporting to Khaz Algar. At one point I thought I’d run out of quests as I handed one in and didn’t see the next one. I highly recommend getting the BtWQuests addon, because I was able to look and see that the next quest came from Moira, even though I didn’t see a quest icon above her, when I clicked her she had the quest. I got back to khaz algar and completed the introduction, so now I have flying, and I bound my hearthstone so I can get back. I am not game to try doing the Catch Up again, but have started going through the regular questing. Hope this helps some people!
Big shout out to my wonderful, patient friend who flew my butt around looking for quests, and was the one who eventually remembered seeing the scroll with the quest!