You need a few things.
The application must be actively listening on the port, if it is not there is nothing to respond.
The firewall on the PC must allow it, try to disable the firewall temporary.
And most important and a common issue is the IP address you see in this tool must match the ip address on the wan on your router. What this means is you must have a public IP. You can look up what are private and public IP but it tends to be simpler just to see if they are the same since the IP you see in tools like this are always public.