'Failed to apply patch'

Hi,

This is the first time I've tried playing anything WoW related.
After logging in on the client, I get a screen saying 'Downloading update' that stays at 0%.
After some time I get a prompt telling me to restart the client and it'll patch the game.
After clicking restart, the game shows me a 'Failed to apply patch'

Is there a fix for this?
Thanks

Log in using your Warmane account name, not email address

Thank you! I feel stupid for not realizing this, but after playing so many games where you have to log in with email I just assumed.