Your account needs to be converted to a Battle.net account

So I was playing Mists of Pandaria yesterday and I just got disconnected. When I tried to log back in it gave me this error:
Your account needs to be converted to a Battle.net account. Please [Click Here] or go to: [https://eu.battle.net/account/creation/landing.xml] to begin the conversion
I tried restarting my game, computer, router, I tried deleting my addons, I tried to delete the WTF folder so that it would create itself again and I just don't know what is happening or how to fix it. Please reply as soon as possible. It would be much appreciated.

get a new client

Do you mean I should re-download from Warmane?

I'm struggling with the same problem, whereas the warmane one isn't working, throwing fatal errors at every start of WoW.exe so I had to go with a different one, turns out - this goddamn error

go here: https://www.warmane.com/account and get "MoP minimal"

It doesn't work for me. Have both clients, stuck on Connecting on both.