Since the routing chain looks correct, this is likely deeper than a basic setup issue and could be a transport handshake issue between Vapi and Telnyx, credential permission scope, or an internal provider-side mismatch not visible in the dashboard. I’d be happy to take a closer look privately and help troubleshoot it properly, because at this point it needs a more detailed review of logs and config. Feel free to DM me if you'd like me to help get it resolved quickly.