400: Bad Request. If you receive a 400 Bad Request error stating “The group must be Active in order to be used,” you need to visit the portal and update the group status to “Active” for proper functionality. Ensure the group is active to resolve this issue.
401: Unauthorized. The credentials are missing or are incorrect. Verify your credentials are correct.
403: Forbidden. Missing information that needs to be included. For example:

{
  "status": 403,
  "message": "Please include opt-out instructions in your message"
}

requires some additional information in the message.