The customer authorization (provided in the link you clicked) is out of date, and does not entitle you to use the Blended Threat service.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/publications/agent-update-brexit-special?utm_source=93d7f0bc-5e92-4f9d-9485-375935947cfa&utm_medium=email&utm_campaign=govuk-notifications&utm_content=immediate