The customer authorization (provided in the link you clicked) is out of date, and does not entitle you to use the Blended Threat service.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/european-temporary-leave-to-remain-in-the-uk?utm_source=de857dee-0234-46c2-91d3-871223c9852a&utm_medium=email&utm_campaign=govuk-notifications&utm_content=immediate