This happened to me a few days ago after casting teleport to guild hall. After clicking yes, I eventually got that message and was back where I started. One time it took 2 more attempts, and another time it took 1 more attempt to get in. My guess is the guild hall instance was taking too long to spin up.
The servers are buggy right now so odd stuff is happening, guild halls hanging, krono delay, slow zoning, stuttering etc. Lots of issues going on. Hopefully after Wed patch it will clear them up.
Been getting that message a lot since the emergency patch a week after LS launched. I just wait a couple of seconds, try again, and it works.