Backup from Android (Moto G)phone fails

I have Norton Mobile Security installed on my Moto G phone, and it lately has been unable to run the backup application. When I try, it at first shows me the App and the number of backed up Contacts and the number of Contacts on device, plus the yellow backup Bar/button. When I press the yellow bar, it goes to the next screen, where it shows the backup file it will be creating, consisting of the current time and date, when I press "submit", it runs for about 2 seconds showing "Backup is Processing", then I get a box that says "Backup Failed try again later". I checked my activity log, and see that the last time a successful backup occurred was Jan 28. The log shows all other events, like live update and malware scans have been successful. Scheduled backups all show as "scheduled backup is postponed because device is active"  I would appreciate any advice to get the backup function working again on my phone.

Thanks,

Bob