I've just recently bought NWN 2 and need to know If I need a specific CD-Key for multiplayer.
If I do I will require one as soon as possible.
NWN2 used to come with the keys you need. Last year that changed & I'm not sure if they fixed it.
Look in your Account> Library >Neverwinter Nights 2 Complete, view downloads, then More, then Serial Keys. See Pic
If it has the three serial keys there.
Then in your NWN2 Complete Folder, look for SerialTool.exe, click on that & copy and paste the Serial Keys into it.
If you don't have the three Serial Keys listed. You will need to contact Support directly and ask them to send them to you. https://www.gog.com/support/contact/technical_issues_with_games/neverwinter_nights_2_complete
If you use Gog Galaxy, then I have no idea how that works.