I'm having trouble connecting a PC through VPN, it happens on Win 10 and Win 7, when you connect using the external IP address it terminates due to PPP, error "The PPP link protocol was terminated". We've reinstalled the RRAS role and configured with still no luck. when you connect it bounces back asking for credentials, even though they are correct it still bounces back asking again for them.
Is there anything we are missing? we are using a draytek 2760 router with all necessary ports open and pointing to the server which is 2012 R2 Standard.
Any help would be appreciated.