16000: Whisper Not Available on Twilio Conference

This error occurs when you try to use whisper or coaching on a standard Voice Conference. Whispering is available only on Agent Conference, and Twilio Conference supports participant coaching in that mode.

• You attempted to set up whisper on a conference that was created without Agent Conference enabled.
• Your account is configured for standard Conference instead of Agent Conference, so the conference leg does not support agent whispering.

• Enable Agent Conference in the Twilio Console conference settings, then create the conference again with Agent Conference enabled.
• Use the Agent Conference coaching flow when you need a supervisor to speak privately to one participant without others hearing the audio.

• Voice Conference
• TwiML Voice: <Conference>