FortiClient 5.4 SSL VPN connection issue on Windows 7

FortiClient SSL VPN connection drops at 40% on hosts with Windows 7 with the following error message:

Unable to establish the VPN connection. The VPN server may be unreachable. (-5)

FortiClient version 5.4.0 and up may presents connectivity issues when installed on Windows 7 hosts.

Make sure that protocols TLS 1.1 and TLS 1.2 are enabled on the host OS. Go to:

Control Panel > Internet Options > Advanced > Security

And check:

Use TLS 1.1
Use TLS 1.2