Webserver not responding to remote users

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We deployed FortiGate 100E in transparent mode, with cisco ASA upstream the FortiGate and a LAN switch behind it. the ASA provides the VPN service to our remote users.VPN connects and remote users can reach some servers on the LAN. However, one of the servers providing services on TCP port 8005 will not respond. 

We have reversed cloned the forwarding ipv4 policy with customized service permitting source port 8005 to ALL. Traces showed "no session matched" when the server attempts to respond to "SYN" request(TCP Shandshake).

We are pretty new to FortiGate. Please, how can we get the server respond to our remote users?