30121: Fallback URL is missing

Twilio returns this error when the Link Shortening domain configuration does not include a FallbackUrl. Link Shortening domain defaults are set on the domain, and Twilio applies them to any Messaging Service that uses that domain.

• You left the Domain fallback URL field blank in the Console when configuring Link Shortening for the domain.
• You sent a POST request to the Link Shortening domain's Config subresource without the FallbackUrl parameter.
• You associated a Messaging Service with a Link Shortening domain, but you did not complete the domain default configuration.

• Open the Link Shortening domain configuration in the Console, then fill in Domain fallback URL and save the changes.
• If you use the API, send FallbackUrl in a POST request to the Link Shortening domain's Config subresource.
• If you also need click tracking, provide CallbackUrl in the same request so the domain default configuration is complete.

• Link Shortening Onboarding Guide
• Messaging Service resource