It starts the "estimating..." and after 3 minutes it fails with "the last backup could not be completed".
iCloud Backup fails
Not the only one. Same issue here. Tried signing out, resets etc and issue prevails.
I was able to backup to my Macbook using iTunes.
Hello,
I have the same problem and I can not delete the backup from iCloud. Now I have 8GB too little. Apple Support told me to contact the Developer Support.