SIP
488 Not Acceptable Here
The request was understood but the session description (SDP) is not acceptable. The response may contain a list of acceptable media parameters.
When You See This Code
When codec negotiation fails — the callee cannot handle any of the codecs offered in the SDP. Common in interop scenarios.
How to Fix
Check the Warning header or SDP in the response for acceptable parameters. Add compatible codecs (e.g., G.711 as a fallback) to your offer.