How to troubleshoot VPN error 806 (GRE blocked) in Windows
When working with a VPN in certain circumstances, errors sometimes occur, especially on Windows 10, one of which is called “806 (VPN GRE error blocked)”. If you see the pop-up, the VPN is not working. The full context of the message reads as follows:
“A connection has been established between your computer and the VPN server, but the VPN connection cannot be completed. Error code 806 – The most common reason for this error is that at least one Internet device (such as a firewall or router) between your computer and the VPN server is not configured to allow Generic Routing Encapsulation (GRE) packets. If the problem persists, contact your network administrator or ISP.”