When you load nwserver.exe, is the "Post Game to Internet" checkbox unchecked? If so, your game is (unsurprisingly) not being posted to the internet. To fix this, change the Gamespy Enabled setting in your nwnplayer.ini file from 0 to 1, save the file, then load nwserver.exe again. The checkbox should now be checked, and when the server is loaded it should be visible on Gamespy. I am not sure if the tutorial mentioned this, since I am not sure what tutorial you are using.