Not able to log into cataclysm classic webpage

Hi, i have tried to log into the cata clasic webpage to be able to opt into the beta but a O.AUTH2.0 error occurs with the web page displaying 400 invalid grant type or callback URL is not valid.
Have tried logging out of everything but can only log into bnet retail but not the classic webpage.
have tried it on edge, chrome and mobile and all the same issue ??