The customer authorization (provided in the link you clicked) is out of date, and does not entitle you to use the Blended Threat service.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/uk-residents-visiting-the-eueea-and-switzerland-healthcare?utm_source=b996d212-8e18-4bcd-84b8-f8913d66f8d3&utm_medium=email&utm_campaign=govuk-notifications&utm_content=immediate