I'm not supporting this but I'm curious, in case there is a problem for my new KM.

The client / general tab is the tag for the client, not the server host/IP. It doesn't matter what it is. The text field next to the connect button is for the server IP/host.

firstly do the server or client give any indication of connection in the log? because if the client fails to connect it should at least give an error message.

Additionally:
I don't know enough about windows firewall to take it not asking for unblock as any proof. If Synergy connects it indicates at least TCP/IP is probably ok (but even still it doesn't prove me that port X is routed correctly just because port Y is). If all else failed I would use telnet to establish the server is listening correctly by
a) connecting to the server via telnet locally (ie telnet localhost <port#>)
b) connecting to the server on your alt PC via telnet also.

telnet is just gonna say .. connection refused or clear the screen if it connects. In case it connects the server will not report a connection, but at least you know the port is open and listening, and your network is ok!