A peril of the digital age: Players who have purchased legitimate copies of The Witcher III on the Xbox One can't play them; they're being greeted with an error message instead. Posts on Reddit and Microsoft's support forum seem to suggest this error occurs only with the digital download version of the game and not the disc-based one.
Note: this is not people being locked out of a multiplayer mode or even DLC, but out of the game altogether.
Surprisingly, this is not even the first time that Xbox One units have locked players out of their games: Earlier this year, some owners of Far Cry 4 encountered a similar problem.
Gamasutra has reproduced the Xbox Live status message for the game as it stands of this writing below. For current status of the game, you can check this link.