You are looking at the event log of the responding device and it says Rejected an initial Phase 1 packet from an unrecognized peer gateway Which is NOT likely reason for the failure?
You have created your tunnel interface in theUntrustzone. Traffic from the Trust zone is able to enter the tunnel and pass to the destination. However traffic from a different interface in theUntrust zone is not able to pass traffic through the tunnel. You are using a single virtual router. What could be causing this problem?