You will see this message if you are trying to connect to a Virtual Private Network (VPN) but are unable to do so. There are a number of reasons this could happen and if you are a VPN user who has no knowledge of the technicalities involved, the best option is to contact the network administrator to resolve the issue. However, if this is not possible, there are some steps you could take to try resolve the problem although in the end, you will often have to turn to the administrator for help.
3 things you should do if Unable to establish the VPN connection
First of all check to see if you are using the correct VPN server name. Check your documentation or contact the administrator for the correct VPN name. The problem could also lie with a non-functioning internet or network connection. To check this click on the start button and type in “ping” (without the inverted comas) and in the window that open you will see if a connection has been established or not. If not you will need to check your connections and modem.
Another problem could be of your firewall blocking access to the VPN. The firewall protects your computer from unauthorized access over the internet and because of this, if it is not properly set up, may block VPN access. Open the firewall (use the Help and Support feature of Windows) if you are not sure how to go about this. Check to see if VPN access is allowed and if not, go to the firewall providers help page (if you are not using the Windows firewall) to learn how to enable VPN access.
If your server has too many clients connected to the VPN, it may block you to prevent overload. This is not a common problem but your administrator will need to check it.
And finally the most common reason for the 800 error is that your router has out dated firmware installed and needs to be upgraded. Once again, you will need to contact your administrator as this is not something you can check yourself.
TipFor more information, please see: How to fix Connection error #800