Some users attempting to update to Apple’s latest iOS 10 on their iPhones and iPads have been left with inoperable devices. There is a fix, but it requires a real computer to do it. Here’s how.
1. Find a computer – Windows PC or Mac – with the latest version of iTunes that supports iOS 10
2. Connect your iPhone or iPad to the computer
3. Open iTunes
4. Press and hold the Sleep and Home buttons on the iPhone or iPad until recovery mode starts and the screen shows a prompt to plug it into iTunes
5. Check iTunes for a prompt to either update or restore the iPhone or iPad
6. Select update to continue with the iOS 10 upgrade (restore will put you back on iOS 9)
7. Wait for the phone or tablet to update and continue setup on the device
Really it works. Maybe that can help to someone!
https://www.theguardian.com/technology/2016/sep/14/fix-broken-ios-10-update-bricked-iphone-ipad-itunes