The following Firewall rules are required for our SIP Overlay product to work without issues;
The following is needed for GS Remote Provisioning (HTTPS):
34.247.234.27
3.248.235.169
TR69 TCP 7547
54.73.211.221
18.168.177.2
18.133.210.75
SIP UDP 5060
18.202.203.180
3.248.235.162
Syslog Server UDP 514
54.78.187.107
108.128.177.46
If these rules are configured and you are still having issues we advise running the phones over an open network to identify whether the issue is related to the router settings, you can also check the call flow within SIP Manager or the SIP Wholesale portal to confirm what is happening with the calls.