Recently I tried playing on the higher ground server. After creating a character I was booted out of the game before the server would load. The error message was "CD Key Authorization denied", it seems I'm not the only one with this problem.
This is the only server I have had this error with and I have already requested Keys from GOG.com which I have been playing with on other servers.
Welcome to hg. Usually this happens if you use the original gog keys which are provided with the installation you bought from them. In such a case you send gog.com an email requesting a set of keys to play online. Once you get those you go into your nwn folder and open the nwncdkey.ini file with a text editor (e.g. notepad). Exchange the keys there with the new ones and you should be able to log in. What still can prevent you from logging in is that you by some random chance use the login of another player. That is blocked and you need to make yourself another personal login. The third option that stops you will be using 'free' keys found in the net. If someone else uses those already u need new ones.