Transparent Web Proxy - FortiOS 5.6

Hi Guys, Before I start, i'm a newbie in configuring fortigate. I've configured fsso using ldap. I've added the user groups of the domain to the user groups in the fortigate. Now I want to configure transparent web proxy to apply web authentication to HTTP traffic accepted by a firewall policy. I've created a IPv4 firewall and then created  a policy that accepts traffic that I want to apply web authentication to. Then I've configured the transparent web proxy.    After doing this I can observe in the log and reports that all traffic is still going through the IPv4 policy but not through the transparent web proxy policy. Did someone also encountered this issue ?   The cookbook that I used to configure the transparent web proxy is the following: http://cookbook.fortinet....nsparent-web-proxy-56/