The customer authorization (provided in the link you clicked) is out of date, and does not entitle you to use the Blended Threat service.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/guidance/broadcasting-and-video-on-demand-if-theres-no-brexit-deal?utm_source=fedda805-4d0b-4cc5-b043-8049a21e732e&utm_medium=email&utm_campaign=govuk-notifications&utm_content=immediate