Hi,
Do 'show security flow session' and check which policy you're hitting.
For example:
When I try to ping 8.8.8.8 from my PC , and do the 'show security flow session destination-prefix 8.8.8.8' command, I see that I'm hitting policy named "1" :
Session ID: 3275, Policy name: 1/7, Timeout: 2, Valid
In: 192.168.1.2/63193 --> 8.8.8.8/53;udp, If: vlan.0, Pkts: 1, Bytes: 74
Out: 8.8.8.8/53 --> 10.0.0.16/24406;udp, If: fe-0/0/0.0, Pkts: 1, Bytes: 90
Can you confirm that you're hitting the policy " from-zone trust to-zone untrust policy default-permit " ?