If you are getting error 789 while trying to connect to VPN, Please try following solutions:
The VPN server is unavailable and thus failing to connect, we suggest trying different VPN locations from the list.
The L2TP protocol is blocked at your network. This is common case if you are connecting to VPN from School, Office or restricted network which blocks VPN usage. We suggest using SSTP or OpenVPN protocol in such case.
You can try restarting your modem/router , as that will change your IP address and may fix the problem.