Windows 11/FortiClient Issue

[shokabeln]

Hello,

Coming to this subject regarding an issue with a Windows 11 device and FortiClient that I can’t seem to resolve.

I have a user who is on Windows 11 and cannot connect to VPN, this was working for them on Monday/Tuesday and then on Wednesday morning they were unable to connect and are getting a ‘Unable to establish the VPN connection. The VPN server may be unreachable (-6005)’

I have done the following in the troubleshooting process and have had no luck:

-Rebooted laptop multiple times -Rebooted home router -Uninstalled/reinstalled FortiClient -Initially they were on 7.0.9 so I tried 7.2.3 with no luck, and I tried 7.0.6 (per support) with no luck -Updated wireless NIC drivers -Confirmed they can connect via the web portal -Checked for any Windows updates that were done. There were some Monday morning but they were able to connect Monday afternoon and Tuesday so not sure this is the culprit.

They are using SAML auth with Entra for authentication.

I also tested this users creds on a Windows 10 machine with 7.0.9 FortiClient and it connected right away. We also tested other creds on the issue PC and got the same results. At this point I opened up a ticket with support and they recommended trying version 7.0.6 which didn’t work. They also recommended hardwiring in instead of wireless but this user doesn’t have the ability to do this. There next recommendation is to downgrade to Windows 10 which the customer doesn’t want to do. That is all support provided to me.

I am having one of our help desk guys reimage the PC but am optimistic that will do anything at this point.

Has anyone else had this issue before or similar and were able to resolve it? It feels like some sort of compatibility issue or something between the PC and FortiClient but that is a little out of my wheelhouse and not sure how to verify that.

Thanks!

[AEK]

In such situation I'd probably do that:

• Check traffic logs and sniffer on local firewall to see if my VPN connection attempts are really sent from my PC and to see if any response from remote firewall
• Check VPN logs and sniffer on remote FG to see if it is receiving my connection request
• Try debug on remote FG:  https://community.fortinet.com/t5/FortiGate/Troubleshooting-Tip-SSL-VPN-Troubleshooting/ta-p/189542