The customer authorization (provided in the link you clicked) is out of date, and does not entitle you to use the Blended Threat service.
https://login.thefa.com/b2cthefa.onmicrosoft.com/b2c_1a_signup_signin_wgswithroles/oauth2/v2.0/authorize?client_id=71fbae14-8952-460b-bc96-d12524391890&redirect_uri=https%3A%2F%2Fwholegame.thefa.com%2FIndividual%2FInvoice%2FSummary&response_mode=form_post&response_type=code%20id_token&scope=openid&state=OpenIdConnect.AuthenticationProperties%3DsDc_M53eGDGx7p_H1aCn4nyWuerB87bZeoPyUbP5Llm8U8kZ3bdr7JhU9EL3TfEVvzW5ANfSVX40vNEmHlAzCboVSyZWpHPoyHrR_VVQAk2rXvyBG3RCVej335PYtp1EiTJ3C8MVwLcFioLFAk1KKYaaUeBogBV5IFaCMNdSjnm5QuyLmEgC30EBMT3KtzOEFgMLvfeTlRnnIi7BQLkY0IHOsus&nonce=637586617079036415.OTdkZDI2MmEtYWUzNC00NTZmLWE1NTItZGU5YWYxYjZjNTVkOTBkMTgxYmEtZjJjMy00OTk2LThkMTMtYmFmNzVkYTVkYmQ1&x-client-SKU=ID_NET45&x-client-ver=5.5.0.0