You’re not alone
The error — coded “0x87de2726” — was confirmed by Microsoft as a licensing issue, and plagued players for several hours… even if they tried to play offline.
Though the Xbox Live Status page has now cleared the error (or, more accurately, it’s been replaced by a problem with screenshot sharing on Minecraft: Xbox 360 Edition), users on reddit and NeoGAF are still reporting issues, specifically with loading and/or installing DLC.
Are you still having trouble with your digital copy of The Witcher 3: Wild Hunt on Xbox One? Let us know!