This message may appear on your BATM’s screen when an SMS could not be sent.
CAS relies on Twilio or Nexmo to send SMS messages. The message is submitted to them, and a verification code is received back when they accept it. The verification code is saved in the Master log.
The message must be formatted properly, and must include a valid phone number (provided by the customer). If the phone number being submitted is indeed valid, then several other possible points of failure come into question.