The API has returned a SUCCESS response but no message was sent
The "response_code" is used to confirm if we received the request and processed it successfully. You can view the status codes here.
You will need to look further down in the response for additional information in the "status_text". You can view our application status codes here.
For example, when using the Send SMS endpoint you may get 'SUCCESS' in the response_code but 'INVALID_CREDENTIALS' in the status_text.