From your post it appears that you’ve ran the command with the wrong syntax. It seems that you’ve ran:
nxupnp.exe -A list 4000 -R <YOUR_PUBLIC_IP> TCP 600
nxupnp.exe -A list 4000 -R <OUTSIDE_PORT> TCP 600
To clarify – the argument after “-R” should be a port that will be opened on your router and made available to access from the outside. So, an example of this command would be:
nxupnp.exe -A list 4000 -R 4000 TCP 600
Could you please try to run it with proper syntax and share the results?