What does the error code 400 Bad Request mean?

The request could not be understood or was missing the required parameters. Verify the request body and parameters to ensure all required fields are present and valid. If switching from pre-production to production, ensure you use the correct client ID, secret, and input parameters. If you're experiencing issues with your production environment's client ID, secret, and input parameters, tell the Vodafone support desk, and we'll fix them.