log in details not matched

I'm trying to log in to the new app. I get as far as the screen that says "success,  all we need now is your id mobile number". When I add the mobile number, last name and date if birth I get a message to say "sorry, your details do not match our records " and I can't progress any further. I've resorted to this forum as there appears to also be an issue with the live chat function not loading. Can anyone help? Thanks