Googling that error shows it’s an issue at the Blizzard end of things to do with a BattleTag not being correctly set with an account. I’m guessing you haven’t played for a while ?
This is detailed here: https://eu.battle.net/support/en/article/65035
Because you can’t get to the Account Settings part of the Blizzard website it may be that you’re unable to resolve this yourself. Some suggestions for you, though:
Try launching the Blizzard Launcher with administrative privileges. This is suggested in the article I linked. I think it’s worth a shot.
Have you tried launching WOW directly from the application rather than through the Blizzard Launcher ? This might get you further into the process - and, try launching it with administrative privileges.
Just in case you’re not sure how to do this, find the application in question and right-click it, and select ‘Run As Administrator’ from the pop up menu.
If none of this helps I think you may have to ask for help. This article details how to raise a ticket when you are unable to log in. https://eu.battle.net/support/en/article/43885