SIP/SDP packet invite issue

  • Hello,
      I really new with PFSENSE product. I configured an IPSEC vpn from 2 site "1" and "2"  and all it is working. The server "A" SITE1 can reach the server "B" on the SITE2 and viceversa (PING) and SIP REGISTER. But if from "A" I sent an INVITE SIP/SDP packets these are received on the IPSEC interface of my PFSENSE server and forwarded on the "LAN" interface (I traced the capture on the LAN interface) but they do not go out from the ethernet port. The impression is that these packet are dropped between PFSENSE "LAN" port and the phisical ethernet card. Firewall is complete open. I am using Version 2.3.3-Release. Could you help me to understand what I can check?
    Thanks a lot