VPN Client Connection With Subsystem Error

Can you fix it please ?
This is a client VPN error, which I receive on my PC where I have VPN client end installed.
Now the server is working fine, all other clients are working fine as well but only two clients are giving me this error.
As in the below image it says, that one network interface should be active and should have an IP.
Error 51: Unable to communicate with the VPN subsystem.
Please make sure that you have at least one network interface that is currently active
and has an IP address and start this application again.
Now can you please tell me why I am receiving this error, while I have all network interfaces working properly. None of them are disabled and all have IP addresses.
Please reply if you know the right answer.
