We have a NEC 8100 phone system. At the main site where the system is we are using a TZ200 at remote site we have a TZ100 with a site to site VPN. The phone rings on the other side but there is no voice between sites. I have opened VOIP ports, plus ports 10000 - 20000 and ports 5080-5081. Sip transfermation is disable on both. Can anyone help me?????