This is saying the hub is able to send traffic but no reply comes back from the spoke.
Session ID: 14513, Policy name: self-traffic-policy/1, Timeout: 56, Valid In: 192.168.3.1/0 --> 192.168.6.5/7738;icmp, If: .local..0, Pkts: 1, Bytes: 84 Out: 192.168.6.5/7738 --> 192.168.3.1/0;icmp, If: st0.0, Pkts: 0, Bytes: 0
Run throught these steps on the spoke side device. You can start at #3
https://kb.juniper.net/InfoCenter/index?page=content&id=KB10093