There might be a time we come across specific issues with backups being unable to be moved to your specified destination. It is in our best interest to try to locate the error that is preventing the backup system from creating a restore point. These factors can vary from a range of items. The best way to identify them would be by reviewing the logs concerning backups.
The logs to review would be the following:
/usr/local/cpanel/logs/error_log
This file contains general cPanel & WHM errors
/usr/local/cpanel/logs/cpbackup
This directory contains the cPanel backup log files.
/usr/local/cpanel/logs/cpbackup_transporter
This directory contains the cPanel Backup Transporter's log files.
After having been able to identify your error, you can then begin to coordinate a solution based on the reported message. If you might have issues with uploading a backup to your destination. A great tool to be able to review the logs, in this case, would be the following command:
grep "Upload attempt failed" /usr/local/cpanel/logs/cpbackup_transporter/cpbackup_transporter.1446102630.log
For example, the reported message:
[2020-05-04 10:37:58 -0600] warn [cpbackup_transporter] Upload attempt failed: 2020-05-04/accounts/tac.tar.gz: Disk quota exceeded
Cpanel::LoggerAdapter::warn(Cpanel::LoggerAdapter=HASH(0x1caa8e0), "Upload attempt failed: 2020-05-04/accounts/tac.tar.gz: Disk q"...) called at /usr/local/cpanel/Cpanel/Backup/Queue.pm line 658
We can see in the above example, that the reported message was about the server having issues with the "Disk quota exceeded." From here, it would be then suggestive to increase the space on your destination server.
More information on backup transportation issues: