1. Understand the SIP Theory
2. Perform the troubleshooting
3. Refer the cases
- One-way audio & NAT related issue
- Internal, Inbound or Outbound Call Failure
- Call Drop or Call Hangup issue during active call
4. Log Capture
If issue persists after you perform the above steps. try to get and post us the logs when you replicate the issue for further analysis.
1) System Log with Debug option enabled.
Here is the guide about how to get the System Log:
Also tick Debug option,
2) PCAP log
Here is the guide about how to get the PCAP capture: