For security reasons, the API token is valid 2 weeks at the time of writing and will be prolongate until 2 months in future. It means you have to authorize and validate that you are the owner of the API token. A message will be displayed in the Magento backend when the API token is not anymore valid.
You will have to use a valid ricardo.ch account to authorize the access to the API
If a problem occur with the API you can also unlink your token by going into the dashboard of the extension, Menu ricardo.ch > Dashboard and click on the button "Unlink" in the token grid.
You can also force the authorization by visiting the page, Menu ricardo.ch > Configuration > Button "Authorization API". Click on it to regenerate the authentification if a problem occur with the API