Hey all,
There are a lot of different causes for "transfer aborted: instance not found: errors, but I did want to call attention to one specific cause that has been reported a few times in this thread.
Our WoW team is working to resolve an issue that occurs primarily after realm restarts/maintenance which can cause this error to show up when travelling to a new zone (either through flying or portaling). The issue does not need any troubleshooting on the user end, as the problem will clear up on its own after a bit of time.
If you find yourself running into this error right after restarts or maintenance this is likely what is happening. The trigger for this error occurs when your game client can’t successfully connect to the server IP address for the world/instance server that you’re being transferred to, so usually it is just a connectivity issue. In this specific case though it is due to the problem mentioned above.
Hopefully the WoW team will be able to get this one cleared up soon, and thanks for the reports!