I’m having the same problem but with all of my characters.
Suddenly I got disconnected and can’t log back on. I can enter the character selection screen and stay there if I want, but when I connect with a character, after the loading, I get insta-DCed.
Already tried with three different connections: my neighbour (which has a differente internet provider than me), my connection and my mobile data connection. None works.
https://us.forums.blizzard.com/en/wow/t/suddenly-getting-wow51900319-and-unable-to-play/731405