The customer authorization (provided in the link you clicked) is out of date, and does not entitle you to use the Blended Threat service.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/brexit-readiness-report-published?utm_source=bc7e11a5-5d4c-48bb-a1a8-dc433fbdef20&utm_medium=email&utm_campaign=govuk-notifications&utm_content=immediate