Can't get my iPad to back up to the iCloud.

I can't get my iPad to back up to the iCloud. My iPhone backs up regularly and there is no iCloud storage space issue. It won't even back up when I hit the "Back Up Now" button. The iCloud Backup button has been selected and the Wifi is working. The message I receive when I hit the "Back Up Now" button is "The last backup could not be completed. Last Backup: Never."