The customer authorization (provided in the link you clicked) is out of date, and does not entitle you to use the Blended Threat service.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://www.gov.uk/government/news/get-ready-for-brexit-campaign-moves-into-new-phase?utm_source=4ad513d0-f19f-495b-8740-1e2e1b7aa023&utm_medium=email&utm_campaign=govuk-notifications&utm_content=immediate