The customer authorization (provided in the link you clicked) is out of date, and does not entitle you to use the Blended Threat service.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/moving-goods-under-the-northern-ireland-protocol?utm_source=31627de8-52d0-43b2-95b4-ed168b616fe2&utm_medium=email&utm_campaign=govuk-notifications&utm_content=daily