Troubleshooting Tip: How to workaround the VPN error 'Unable to establish the VPN connection . The VPN server may be unreachable. (-5052)'

[M_Abdelhamid]

Description	This article describes how to proceed when having an issue with the FortiClient connectivity to FortiGate or FortiSASE.
Scope	FortiClient, FortiGate, FortiSASE.
Solution	On some Windows machines, the user might have the error 'Unable to establish the VPN connection. The VPN server may be unreachable. (-5052)' while trying to connect to the FortiGate or FortiSASE using the FortiClient VPN. Run the basic connectivity steps: Verify network connectivity. Check VPN server settings in FortiClient. Disable firewall and antivirus temporarily. Update FortiClient to the latest version. Flush the DNS cache using the command 'ipconfig /flushdns'. Remove any conflicting VPN or networking software. Isolate the cache issues: Rename the folder C:\Users\<user>\AppData\Local\FortiClient to provide it with a name. Re-connect the FortiClient to the FortiGate or FortiSASE (FortiClient will automatically create a new folder C:\Users\<user>\AppData\Local\FortiClient) Note: In step 1, the user can delete the file at all. However, it is recommended to rename it and keep it for further analysis or rolling-back, if needed. If the error 'Unable to establish the VPN connection. The VPN server may be unreachable. (-5053) is encountered, see Technical Tip: Unable to establish the VPN connection: 'The VPN server may be unreachable. (-5053)' for troubleshooting steps. If the issue persists, contact Fortinet support for further assistance.