SIP 488 Not Acceptable Here
TwilioRFC 3261 §21.4.26The destination accepted the request but cannot honour the SDP offer. The classic codec-mismatch error: the offered codecs don't intersect the callee's allow-list.
Common causes on Twilio
- Codec mismatch (e.g. caller G.722 only, callee G.711 only)
- Transcoder offline or not configured
- SRTP required by one side but TLS/SIPS missing
- Wrong RTP IP/port from a NAT-broken UA
Stop guessing — paste your trace
Drop your PCAP or sngrep log and SIP Flow will render the ladder, surface the failing transaction, and (optionally) ask Gemini to suggest the fix grounded in Twilio docs.
Open analyzerDon't have a trace yet? See how to capture one in Wireshark, sngrep, or your PBX