Situation

# 忘記IPsec Pre Share Key
Forgot IPsec Phase1 PSK

Solution

[1]
Login FortiGate WebUI.

[2]
https://"Your_FortiGate_IP"/api/v2/cmdb/vpn.ipsec/phase1-interface?plain-text-password=1

[3]
search for "IPsec_name" > "psksecret"