The error might be reported during backup (VSS-Aware backup sets): "The system cannot find the file specified. (\\[Server_Name]\ADMIN$\complusbackup\[XXXXXXXXXXX]\sfcfiles.lst)" ,
where [Server_Name] is the backup source Server name;
[XXXXXXXXXXX] is the backup session ID#.
Remote Scheduled Task Management is not allowed through Windows firewall in the computer attempted to be backed up.
Enable Remote Scheduled Task Management service on the backup source Windows Server:
Control Panel > Windows Firewall > Allow an app or feature through Windows Firewall > highlight "Remote Scheduled Task Management service" and tick the check-box for the network profile used for backup ("Domain", "Private" or "Public")