Reference

https://docs.fortinet.com/document/forticlient/7.4.4/windows-release-notes/683433/special-notices

Situation

# 7.4.3版本以後沒有免費的VPN-Only FortiClient可以用
The free VPN-only FortiClient is no longer available starting from version 7.4.3.

Solution

# Fortigate設定IPsec IKEv2 > Windows內建VPN新增IKEv2
Configuring FortiGate IPsec IKEv2 for Windows Native VPN Client