The customer authorization (provided in the link you clicked) is out of date, and does not entitle you to use the Blended Threat service.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/exporting-excise-goods-to-the-eu-in-a-no-deal-brexit?utm_source=f340a712-083e-43cd-afee-ec642218a101&utm_medium=email&utm_campaign=govuk-notifications&utm_content=immediate