If you have upgraded to iOS 9, then you are getting this issue with iCloud Backup. iCloud latest backup status indicates "Never" even though iCloud backup was successfully performed before the iOS 9 upgrade. When you want to backup photo and video, you will see error messages such as "The last backup could not be completed" or "iCloud Backup Failed. There was a problem enabling iCloud Backup" or "Not Enough Storage". This iPhone can not be backed up because there is not enough iCloud Storage available".

1. To fix this issue, you can reset Network Settings. If you want to reset Network Settings, then tap "Settings" and tap "General", then tap "Reset" and then tap "Reset Network Settings".
2. You can delete older backups which you don't need. To delete old backups, go to "Settings" and tap "iCloud" then tap "Storage" and then tap "Manage Storage".
3. You can reset your device. to do so, hold down the Home button and the sleep/wake button together until the screen goes back and you see the Apple logo.
4. If you get an iOS update, then upgrade your device.
5. Backup your device using iTunes and do the steps given: Go to "Settings" on your device. Tap "iCloud" and tap "Storage" and then tap "Manage Storage". Select your device that you are unable to backup and then tap "Delete Backup". Once you have deleted the backup, tap "Settings" and tap "iCloud" and then "Backup". Move the slider from right to left tu turn Off "iCloud Backup" and then tap "Back Up Now".

Quick Tip to ensure your Photos never go missing
Photos are precious memories and all of us never want to ever lose them to hard disk crashes or missing drives. PicBackMan is the easiest and simplest way to keep your photos safely backed up in one or more online accounts. Simply download PicBackMan (it's free!), register your account, connect to your online store and tell PicBackMan where your photos are - PicBackMan does the rest, automatically. It bulk uploads all photos and keeps looking for new ones and uploads those too. You don't have to ever touch it.