"Last backup could not be completed" iPhone 6s Plus
I have one backup that completed on my iPhone 6s Plus. Since then, every time I check to see if the phone backed up, I see the message "Last backup could not be completed". The other devices I own do not have this problem. They are backing up to iCloud just fine.
All my devices are up-to-date with the latest version iOS 9.1.
Any suggestions as to how to get the backups working again?
iMac, OS X Mavericks (10.9)