Unable to backup to iCloud.
iPhone 6s, iOS 10
See if this helps -- If iCloud Backup couldn’t be completed or you can’t restore - Apple Support
already been through that article. I have enough storage, around 47GB. Still facing the same problem.
Just wanted to make sure it wasn't a bug because of the iOS 10 update.
What about trying one of two things - try this first one - Restart your iPhone, iPad, or iPod touch - Apple Support
Unable to backup to iCloud.