The destination rejects the media offer or selected SDP parameters.
Likely causes
- No common codec
- SRTP required or forbidden
- Incompatible DTMF mode
- SDP rewritten by SBC/NAT
Checks in priority order
- Capture the INVITE and 488 response
- Compare codecs
- Check SRTP/RTP requirements
- Retry with a minimal media offer
When to escalate
Escalate when the failure affects multiple users, a production dependency is unavailable, or logs show a component outside your control. Include timestamps, scope, tests already performed, and the last known working state.