My problem started after October 3rd. My iPad backed up every night while I charged it over night.
Then on October 17th I received the message that my iPad had not backed up in 2 weeks. At first I figured I must have been doing something wrong for the past two weeks when I plugged it in to recharge and back up. So I reviewed the steps and plugged it in the evening of October 17th, expecting that it would back up over night.
When I awoke on the 18th I discovered that my last back up date was still October 3rd. I tried a manual backup and got the eternal spinning, walked away from the iPad (it was plugged in to the wall) and thought I would check it later. When I checked back about 20-30 minutes later received a message that the back up had failed.
That's when I decided to google for backup failures and found this thread. Since that time I've tried many, many things. I've completely deleted my past back up and turned off everything from my back up data list except for my Contacts, Calendars and Reminders.
I'm now trying to backup with my iPad connected to my computer, again, all data removed from iCloud and trying to back up only my Contacts Calendars and Reminders.
It still doesn't look promising as I type this message. I have the eternal spinner thing going on right now and no extimate for how long the backup will take.
FYI, when my issues began I had used only 2.6 GB of my 5 GB of iCloud storage. So I know that the size of my backup cannot be the main issue. Right now, just trying to back up my Contacts, Calendars and Reminders I show 4.9 GB available.
This is sooooo frustrating because I can't seem to find a viable solution.