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Retell AI

From what you’re describing, this points to a SIP routing or signaling failure before the call ever reaches Retell, which explains the absence of logs on their dashboard.
The repeating 180 Ringing without a 200 OK usually indicates the INVITE is being handled by an upstream SBC or looping, not terminating at Retell’s SIP edge.
Methodically, I’d validate the exact Request-URI, To/From headers, transport (UDP/TCP/TLS), and codec offer against Retell’s inbound SIP requirements, plus confirm no carrier-side timeout is forcing the busy tone.
Can you confirm the precise SIP destination (domain/IP + transport) your provider is sending the INVITE to?
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