Logged off because Account Information Changed: ..What?

[Zungar-silver-hand (Zungar)]

Here’s your other reports…

Error: BLZ51900062 - Account info changed

I’d just finished a Torghast run with some Guild friends, everyone else logged for the night or to do other things whilst I changed my Legendary piece and went back to Oribos to transmog in the Hall of Curiosities. Whilst checking out the helm appearances, I was suddenly booted from the game with the message; “You have been disconnected because your account information has changed. (BLZ51900062)” This of course makes no sense. I have a physical authenticator tied to my account and was playing…