It seems that you're using an outdated browser. Some things may not work as they should (or don't work at all).
We suggest you upgrade newer and better browser like: Chrome, Firefox, Internet Explorer or Opera

×
If anyone comes across this problem now. GOG will put your CD keys in the game files, but there can be problem when these files are generated.

So if there is no Key in DOOM 3/base/doomkey or its just a part of the key just repair your game files and it should work. Also the game shouldn't ask you anymore for your keys.