The customer authorization (provided in the link you clicked) is out of date, and does not entitle you to use the Blended Threat service.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/customs-procedures-if-the-uk-leaves-the-eu-without-a-deal?utm_source=e5753d39-d87b-45dd-a4d6-4130544bb188&utm_medium=email&utm_campaign=govuk-notifications&utm_content=immediate