Troubleshooting Fortigate using CLI

First check if and how traffic enters the device. Use the filter option.

Then check the flow through the firewall and find out the policy id

session info: proto=1 proto_state=00 duration=96 <snip>
misc=0 policy_id=3 auth_info=0 chk_client_info=0 vd=0
<snip>
total session 2

Then use show firewall policy <id> to list the policy used for the traffic:

FGT60ELexThuis # show firewall policy 3
config firewall policy
edit 3
set name "Lex"
set uuid d42a3556-cb66-51e7-e20b-6be8577def0b
set srcintf "internal"
set dstintf "wan1"
set srcaddr "Lex zolder" "Laptop Lex" "PC Huiskamer"
set dstaddr "all"
set action accept
set schedule "always"
set service "ALL"
set utm-status enable
set logtraffic all
set av-profile "Quick block"
set ips-sensor "protect_client"
set application-list "block-botnet-monitor"
set profile-protocol-options "custom-default"
set ssl-ssh-profile "certificate-inspection"
set nat enable
next
end