So the problem is solved, but it was more convoluted than I thought. The last reply by Karma led me into the correct investigative path. First off-- good catch! But it’s greyed out even before I launch the server, I can’t check it either way.
However, after a little research and trying to read between the lines from other people who had this problem: this is how I solved it.
I opened my nwnplayer.ini
Changed:
GameSpy Enabled=1
And now this box is automatically checked (despite still being greyed out), and my server now appears on this list when I launch it - https://nwn.beamdog.net/
So, awesome 
Thank you very much guys, this problem was stifling me and preventing me to progress with my gameworld development. Thank you @Karma!