ForitClient VPN 7.4.3.1790 cannot connect VPN via Proxy

Hello GLD, 

Thank you for using the Community Forum. I will seek to get you an answer or help. We will reply to this thread with an update as soon as possible. 

Thanks, 

Hi @GLD ,

It appears that FortiClient VPN version 7.4.3.1790 has issues when connecting via a proxy server, as you've observed. This behavior aligns with reports from other users who experienced similar problems with version 7.4.1, where the VPN client attempted direct connections instead of routing through the configured proxy, leading to connection failures .​

https://community.fortinet.com/t5/Support-Forum/FortiClient-7-4-1-windows-cannot-connect-to-VPN-via-Proxy/m-p/364166?utm_source=chatgpt.com

Notably, the release notes for FortiClient 7.4.3 do not explicitly mention proxy-related issues . However, the absence of such information doesn't rule out the existence of the problem, especially given user reports.

https://docs.fortinet.com/document/forticlient/7.4.3/windows-release-notes/573433/new-known-issues?utm_source=chatgpt.com

If you can share the logs collected after following the debugging steps and running the relevant commands (as outlined in the link below) on both the FortiClient and FortiGate firewall, we’ll be able to perform a more accurate technical analysis to help resolve the issue.

https://community.fortinet.com/t5/FortiClient/Troubleshooting-Tip-Collecting-logs-for-addressing-VPN/ta-p/362101

BR.

If my answer provided a solution for you, please mark the reply as solved it so that others can get it easily while searching for similar scenarios.

CCIE #68781

Tested the new version of FortiClient 7.2.11 released in July 2025 but still cannot connect via proxy with different symptoms.

• It will stop at 98% for around 30 sec.;
• The FortiClient login screen will be displayed with the login credentials cleared and stop at 45% for around 5 sec.;
• Error box with "Credential or SSLVPN configuration is wrong (-7200)" prompted;
• Packet capture showed the FortiClient will first establish connection DIRECTY to the VPN gateway without going through the proxy AND then establish another connection through the proxy server. 
• TLS hand shacking (Client Hello, Server Hello etc) is only found in the traffic through the proxy.
• For the direct connection, only below packets found:

client              >    vpngateway     TCP   SYN

vpngateway  >     client                 TCP   SYN, ACK

client            >  vpngateway       TCP    ACK

client            >    vpngateway     SYN

vpngateway  >     client                 SYN, ACK

vpngateway > client               TLSv1.2 Alert (level: fatal, Description: Decode Error) 

vpngateway  > client              FIN, ACK

client               >    vpngateway     SYN

vpngateway  >     client                 RST, ACK

Hi @GLD,
Can you help share the FGT config, issue related debugs/sniffer, TAC case if any to sferoz@fortinet.com for more investigation.
Thanks.