Hi @Suy Peang ，
To troubleshoot this issue, we recommend you check it from the following ways:
1.Firewall ports: please make sure you have opened these ports (UDP 3478, TCP 443, UDP/TCP 50000-59999). The following picture shows these ports for your reference:
2.DNS Records: please make sure you have these records(access.<sip-domain>, av.<sip-domain>,conf.<sip-domain>) on your edge server.
3.Certificates: you can refer to the following picture to check you have these certicates SAN on your edge server.
4.Reverse Proxy server: you also need to deploy this server in your topology. For more details about how to deploy it, you can learn it from:
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