The most common error messages regarding binary backups are:

• Mikrotik ERR: Failed to save system configuration backup
  Mikrotik ERR command: /system backup save name="ispadmin"
  If binary backups don’t get saved, first check if the account used by ISPadmin for router configuration has FULL rights. If not, binary backups cannot be used.

• scp timed out while trying to connect to ip_address
  This error implies that ISPadmin cannot log into the router via SSH. Verify SSH access manually. If you are able to connect to router via SSH manually, yet binary backups do not work, the problem might be in connection via SCP. Reinstall OpenSSH client to fix problem with binary backups. To do so, run
  
  apt-get remove openssh-client; apt-get install openssh-client openssh-server ssh

You will find more information on router backups in Other Backups Routers.