Can not see SIP traffic

Hi people, this is my first question and I' m new in fortigate world. We have two sites connected through a dedicated link. There is a 200B FortiGate between these two sites. I have succesfully created policy rules for traffic between sites for allowed protocols. There are two VoIP phones (Yealink tp20p) connected in the remote site that have registered succesfully in VoIP server (Asterix). I' m trying to configure traffic shaping for VoIP according to the following article: http://docs.fortinet.com/fgt/handbook/40mr3/fortigate-traffic-shaping-40-mr3.pdf with no succes. I' m monitoring firewall traffic, but I can' t see SIP service traffic. The only traffic that I can see is one called: " 3/3/ICMP" , working in 711 port. I tried disabling sip-helper with the same result, can' t see SIP or RTP traffic. Anyone can help me? any ideas? Thanks in advance.