21711: Sender is not associated with the specified Messaging Service

You tried to use a phone number, short code, or Alphanumeric Sender ID with a MessagingServiceSid, but that sender is not associated with the Messaging Service you provided. When you send with both MessagingServiceSid and From, the From value must come from that service's Sender Pool. If you omit From, Twilio selects an eligible sender from the Sender Pool for you.

• You included both MessagingServiceSid and From, but the From value is not in that Messaging Service's Sender Pool.
• The sender was never added to the Messaging Service.
• You are trying to send with a sender type that must first be associated with the Messaging Service, such as a phone number, short code, or Alphanumeric Sender ID.

• Add the sender you want to use to the Messaging Service Sender Pool. You can add phone numbers, short codes, and Alphanumeric Sender IDs to a Messaging Service by associating those resources with the service.
• If you send with both MessagingServiceSid and From, update From so it matches a sender that is already associated with that Messaging Service.
• If you do not need to force a specific sender, remove the From parameter and let Twilio choose an eligible sender from the Messaging Service's Sender Pool.
• If the Messaging Service does not have a sender configured yet, add at least one sender before retrying the request.

• Get started with Messaging Services
• Messages resource
• Services PhoneNumbers subresource