If Steam, try uninstalling NWN:EE and reinstalling it, (subscribing to the necessary ravenloft and cep packages from the workshop), to make sure that your CD key has been retrieved properly.
Do not replace your .ini files with your old NWN game, as those CD keys won't be valid for NWN:EE. Copy & pasting files is a common way people might accidentally invalidate their keys.
If it's still not working for whatever reason, run through the exact steps you went through to reach this point, in detail. Maybe someone can pick up on what you did differently from everyone else that's interfering with your bought NWN:EE key.