The customer authorization (provided in the link you clicked) is out of date, and does not entitle you to use the Blended Threat service.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/healthcare-for-eu-and-efta-nationals-living-in-the-uk?utm_source=9c15fdd2-ed25-4c11-8b73-1206651699d6&utm_medium=email&utm_campaign=govuk-notifications&utm_content=immediate