The customer authorization (provided in the link you clicked) is out of date, and does not entitle you to use the Blended Threat service.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/export-licences-and-certificates-from-1-january-2021?utm_source=ff1300f0-6364-48d0-907f-bd4316d7851b&utm_medium=email&utm_campaign=govuk-notifications&utm_content=daily