If you usually power up you're Xbox One by using the " Xbox On" voice command, don't be alarmed if it wont work for you today , its because Microsoft are releasing a mandatory update to fix issue in the OS. If you use 'Instant On' on you're Xbox One , it will have automatically downloaded the update before powering off. After completion of the download you will be required to manually power the Xbox One back up. So dont go arguing with the Xbox One like a wally! For more information, read here.