You need to  ensure your have a IGMP subscription and that a IGMP query enable for that subent.
 
 > if the iptv host is a unix box, the netstat -g cmd will show your subscriptions
 
 
[emnoc@venusfly ~]$ netstat -ng
 IPv6/IPv4 Group Memberships
 Interface       RefCnt Group
 --------------- ------ ---------------------
 lo              1      224.0.0.1
 eth0            1      224.0.0.251
 eth0            1      224.0.0.1
 lo              1      ff02::1
 eth0            1      ff02::fb
 eth0            1      ff02::1:ffc4:be1a
 eth0            1      ff02::1
 eth5            1      ff02::fb
 eth5            2      ff02::1:ff40:8112
 eth5            1      ff02::1
 eth6            1      ff02::fb
 eth6            1      ff02::1:ff40:80a5
 eth6            1      ff02::1
 eth7            1      ff02::fb
 eth7            1      ff02::1:ff40:80a4
 eth7            1      ff02::1
 eth8            1      ff02::fb
 eth8            1      ff02::1:ff40:80a7
 eth8            1      ff02::1
 
 
 > for windows, I don' t know of any reasonable way to find your subscriptions
 
 Next,
 
 To look for a  igmp querier,  execute  the following;
 
 
 tcpdump igmp 
 
 or  for wireshark you can use a display filter of igmp also. I guess you could do the same on the diagnostic packet sniffer on the FGT and specify the lan interface  where the IPTV host(s) sits.
 
 btw: If you have no querier , than this is going to break your multicast_forwarder. Also, if you have a l2 switch that support igmp-snooping, this would break also.