RADONAR: i have the same error with the witcher 3 game of the year edititon. in 2018 i bought the game, and inside the disk box. i had a GOG.com Game Code. i entered the code in my pc, it crashed(bc i had a bad pc back then. and it told me to enter that code while launching the witcher 3) and after i logged in again, i entered the code again, and it told me that the code is used by someone else. i taught that that someone was me, but the game wasnt in my library. imagine haveing 14 hrs in a game you dont own:)). i launched the game by using the shortcut, not the launcer

Carradice: So where did the OP purchase the code?