Refer to the exhibit.

Why did FortiGate drop the packet?
Refer to the exhibit.
Why did FortiGate drop the packet?
The FortiGate dropped the packet because it matched the implicit firewall policy. In FortiGate, 'policy 0' refers to an implicit deny-all policy that drops any traffic that does not explicitly match any configured allow rules. Therefore, the packet did not match any explicit firewall policies and was denied by this implicit default policy leading to the drop.
Policy 0 indicates its the packet was dropped by the default implicit deny
A: https://www.reddit.com/r/fortinet/comments/lg1hkk/msgdenied_by_forward_policy_check_policy_0/