Sorry, this is a weird one that I’d post on the WoW forum but I can’t! It says I need to have at least one level 10 character to post on any forum over there.
I do have many, across three accounts. All three show no characters once I log in. I’ve tried resetting my browser and using another browser with the same results. If it’s happening to me, it’s probably happening to other people who got logged out also!