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Unable to connect fortissl vpn

Hi, I have a peculiar problem while trying to connect using fortissl vpn client. The firewall firmware is v5.0,build3608 (GA Patch 7). When I am trying to connect using the fortissl vpn client (ver. 4.0.2250), I get the message " Unable to establish the vpn connection. The vpn server may be unreachable (-5)" . I have no issue accessing the portal on port 10443. The page gets loaded from my laptop confirming port is not restricted, but it does not connect only i am trying to connect using the ssl vpn client. Parallely, when I try to connect another location firewall (v4.0,build0346,120606 (MR2 Patch 12)) I have no issues as i am able to connect using the same fortissl vpn client. Any ideas as what could cause such issues. There are other clients, who connect to the same firewall (v5.0,build3608 (GA Patch 7)) and using the same fortissl client (ver. 4.0.2250), they have no issues connect to it.



Possibly you' ve already checked this but try disabling Windows Firewall and any other AV/Malware products you have running to ensure they' re not blocking access to that uncommon port.
New Contributor II

Assuming you are using the lite client, have you tried to specify the port in the Server Address: field? The full client provides a field to specify the port you are using for sslvpn. The lite client doesn' t have that field so I have to specify Hopefully it is that simple.
Network Engineer
Network Engineer

Hi, The issue has been resolved. Root Cause: After the firmware upgrade to 5.0.7, it is mandate that the client' s Internet Explorer' s version should be abloe 7.0. Soon after the IE update, it starting connecting.



i had had the same problem this worked 

New Contributor

A new lesson.. Thanks!
Nihas [\b]
Nihas [\b]
New Contributor

Today i faced same problem, v5.6.0 build1449 (GA), Windows 10 PRO 64bit (7 Pro), FortiClient

Some of VPN users cannot connect to SSL VPN, getting "Unable to establish the vpn connection. The vpn server may be unreachable".

Any ideas? 

SSL VPN tunnel was working fine from the start 2-3 month stable.

I've got ident. PC with same configuration and connecting to tunnel without any problems. (Internet Explorer settings ident.)



Turn Off Firewall

Turn Off Antivirus

Restore Fortigate backup to date when all was working, but i have same error, so i guess its not Fortigate side.


Hello everyone


Recently I had the same issue with FortiClient and it was fixed enabling the following options inside of Control Panel/Internet Options/Advanced Options:


- Use SSL 2.0

- Use SSL 3.0

- Use TLS 1.0

- Use TLS 1.1

- Use TLS 1.2




i Getting this error when i try to connect from the forticlient from IPSec

"unable to reach tunnel gateway/policy server"


Please help 

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