Symptom:

You see something like the following error message in the Message Logs of the backup:
"FileIO JobId 1435: ESEBackup: BackupSetup failed error c80001f9: Backup is already active."

Resolution:

This error message typically indicates NTBackup or another backup system is already running on the server. Please make sure all other backup processes have been disabled before running a backup with the CFA.
It is not recommended to back up the same servers with multiple systems/software.