If your VAPI SIP integration isn't working, here are a few quick things to check: SIP Credentials: Double-check that your SIP username, password, and server address are correct in the VAPI dashboard or API setup. Firewall/NAT Issues: Ensure your server or device allows SIP traffic (typically UDP ports 5060 and 10000–20000 for RTP). WebRTC Mode Conflict: VAPI often defaults to WebRTC. If you’re using SIP, make sure the integration mode is explicitly set to SIP in your VAPI agent settings.