UPDATE: It works now. If you bought The Witcher 3 digitally on Xbox One, there’s a chance you can’t play the game right now. There’s a licensing issue—error “0x87de2726”—that’s preventing the game from booting up, but Microsoft is aware of the problem and working on it.
It’s apparently a licensing issue. There’s no timetable for a fix, but hopefully it’s pretty soon.
You can reach the author of this post at patrick.klepek@kotaku.com or on Twitter at @patrickklepek.