Cause: The Campaign Token is incorrect or the form endpoint has changed.
Fix:
In GetResponse, go to your forms and regenerate the form HTML.
Look for the webform_id hidden field value in the form code.
Copy this value and re-enter it in the GetResponse Legacy card in the plugin.
Test by subscribing with a test email address.
Tip: If you are having persistent issues with GetResponse Legacy, consider switching to the standard GetResponse (API) connection instead. It offers more features including list fetching, dayOfCycle support, and server-side subscription.