Could be a routing/networking issue. You should be aware that if you forward a port in your router/modem, it can only be used by one computer in the network; ie: any other computers should have separate ports opened for them. So computer A has port 6346 opened for it. Comp B has a different port opened for it (eg: Port 6342 or something) & any others would also require a separate port no. Also for port forwarding you require a Static ip. A dynamic ip won't work for port forwarding. If port forwarding was set up whilst a dynamic ip was active then you will have to go back & start again. ie: cancel the other PF job. 1. Set up a static ip. 2. Forward a port. 3. Manual port forward instructions & sample image & 2 posts after that.

Should also try to connect whilst LW is not active on the other machines (otherwise they might steal the necessary bandwidth & activity/energy of your router.) At least whilst you're initially trying to connect for the 1st time on the laptop.