I’ve set up a VPN Server on a Windows Server 2012r2 which I usually access from my iPhone or Macbook pro. Once the correct ports are forwarded it was pretty simple and always worked. I recently tried to connect from my Windows 7 machine and my Windows 10 machine both without success.
The Windows 7 error was:
809: The network connection between your computer and the VPN server could not be established because the remote server is not responding…
and the Windows 10 error was:
File Metadata optimization is already in progress.
For this test my server was behind a NAT but the clients were not. Since neither the iOS or MacOS systems were behind a NAT, I felt that the network configuration of the server was not contributing to the error. Nevertheless, I searched for ‘errors’ ‘nat’ ‘vpn’ and I got a hit for at Client behind NAT devices.
I made the following registry change specified in the post for both the Windows 7 and Windows 10 client machines:
Data Value: 2
Then rebooted each system and they both now connect to the VPN server.