The customer authorization (provided in the link you clicked) is out of date, and does not entitle you to use the Blended Threat service.
http://www.acumen.hmrc.gov.uk/_/app/emailRobot/index/click/secret/1db5ab571ae085657d33929d333065cb?link=https%3A%2F%2Fwww.gov.uk%2Fgovernment%2Fpublications%2Ffurther-businesses-and-premises-to-close