vpn ipsec side to side issue

Hello I configure a VPN Site to Site between  network A and   network B the network A has a FortiGate 100D and 60 C for the network B The tunnel up but we have the following result:   -  hosts network A ping the hosts network B.   -  hosts network B not ping  hosts the network A   - If I run the command execute ping [host_A] from the network B in  (FortiGate C) I have an answer   - In the rules of the FortiGate 60C the counter of the output rule: lan ---> vpn interface --->  addr_vpn_local        ---> addr_vpn_remode packet is 0/0 kb

routers version is v5.2.4, build688

attached the network topology

Sorry for my english