the other issue can be a lack of network path between the two machines. this can happen if you have a software firewall blocking incoming traffic or your machines are on different sub nets without proper routing.

to check whether or not your machines are on different subnets, look at the ip address on each keyclone titlebar. if the first 3 numbers don't match (ie: 192.168.0.X != 192.168.3.Y) then you have different subnets. this can happen if you have multiple routers on your LAN.

if that is not the problem, then the odds are your software firewall is blocking. look to open the keyclone port. you could do a manual STUN by clicking connect on both machines at the same time connecting to each other (odds are low you need to do this these days)... tricking the routing tables into thinking a response is coming in from the outgoing request.

of course, this all pre-supposes your have a valid license on each machine.