iCloud "the last backup could not be completed" error message

[striders]

I used iCloud backup for both my iPhone 6+ and iPad Mini 3 and the backup has been successful for months. I never synced both of my device to iTunes in my MackBook.

Yesterday, I connected both of the devices, NOT synced it, but to do manual backup. The iTunes backup were successful. However, I noticed that iCloud backup is now DISABLED.

The problem is, when I turned on iCloud backup again, the iCloud backup ALWAYS FAILED with message "The last backup could not be completed".

Can anyone help me? Or iCloud backup is incompatible that once I did an iTunes backup, the only way to turn it on is to reset the devices?

 

[striders]

Well, now I got a new iPhone 6S Plus and iPad Mini 4 and I can't do iCloud restore.

Now I am afraid to do a restore from iTunes because I don't want more trouble. I.e. The iCloud backup failure happened after I did a backup, for the first time, on iTunes.

Great, now I lost some important data. I.e. 2 Factor Authentication for most of my services have to be re-done since I can't backup the Google Authenticator data.

 

[striders]

Btw, if you have Apple Watch, the data is backed up on your iPhone. So if you don't restore, you'll lost all the Apple Watch data.

Wonderful....