The ~ is your home directory which on RedHat based system is /home/admin So the error above is saying that this directory does not exist /home/admin/admin/user_backups
What are the permissions and who owns those directories?
Why are they admin/admin and not just /admin? I'd make a simple guess and say that the backup program is looking for /home/admin/admin_backups not /home/admin/admin/admin_backups.