Finally, some of the impacted users who are attempting to use recovery or restore mode to restore the iPhone or iPad may encounter an error 1671 or similar error message in iTunes, which further complicates the trouble. The 1671 error may be resolved simply by waiting until the Apple servers can be contacted successfully again. There are also mixed reports of resolving iTunes error 1671 by restarting the iPhone or iPad and the Mac or PC.
If you are experiencing trouble with the iOS 10 update, or you have fixed any iOS 10 update problem, let us know in the comments!