For some reason after reinstalling the Windows server (after a total array failure) the system will no longer allow incoming VPN connections due to failing to allow in GRE packets, from memory all settings for the VPN (Routing & Remote Access) are the same..
The firewall & NAT rules are all ok as it can make a connection to log this message on the server and (PPTP) GRE IS enabled (as well as L2TP) to the same internal IP addresses.
Event Type: Warning
Event Source: Rasman
Event Category: None
Event ID: 20209
Time: 9:54:36 p.m.
A connection between the VPN server and the VPN client (**remote IP address**) has been established, but the VPN connection cannot be completed. The most common cause for this is that a firewall or router between the VPN server and the VPN client is not configured to allow Generic Routing Encapsulation (GRE) packets (protocol 47). Verify that the firewalls and routers between your VPN server and the Internet allow GRE packets. Make sure the firewalls and routers on the user's network are also configured to allow GRE packets. If the problem persists, have the user contact the Internet service provider (ISP) to determine whether the ISP might be blocking GRE packets.