I would blame the router, so I tried a different router (and older SonicWall), set up the tunnel (IPSec) with the same results.

I've tried every setting in Remote Desktop I can find - disabling auto-reconnect, enabling/disabling NLA, firewalls, and quite frankly, I'm stumped. No changes were made to the router, what-so-ever, in that time period (Netgear UTM25) and the tunnel(s) work just fine for file transfer, ICMP, FTP, HTTP(s) - ONLY Remote Desktop is affected. I canĬonnect within the network just fine to all these machines and can connect from outside the VPN (after opening a port on the router) with no problems (though, that is a security risk) as well.

A couple of months ago, I started getting the error message 'An internal error occurred' when connecting through an IPSec tunnel to all Windows 10 machines, a Windows 7 machine and a Windows 2008 R2 server machine.