Forticlient VPN 628 error on Window 10 PC

Running Windows 10 and using Forticlient 6.0 to make an IPSEC VPN connection to our Fortigate 100D. When we attempt to launch VPN before login and authenticate with LDAP user, we get the error "Error 628: The connection was terminated by the remote computer before it could be completed."

If we log in as the local user and then run the VPN, we can authenticate with our LDAP credentials. Have tried several settings suggested by tech support, but no luck.