The customer authorization (provided in the link you clicked) is out of date, and does not entitle you to use the Blended Threat service.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/the-food-and-drink-sector-and-preparing-for-eu-exit?utm_source=af1710b2-26d6-4f7b-8deb-673a15de15fd&utm_medium=email&utm_campaign=govuk-notifications&utm_content=immediate