13218: Dial: Invalid sequential value

The sequential attribute on <Dial> only accepts true or false. Setting sequential="true" lets Twilio call up to ten agents one after the other, in the order they are specified in the verb.

The sequential attribute on <Dial> was set to a value other than true or false.

• Update the <Dial> verb so sequential is set to either true or false.
• If you need sequential dialing, set sequential="true" on <Dial> so Twilio calls up to ten agents one after the other in the specified order.

• TwiML Voice: <Dial>
• Error and Warning Dictionary