ACO6101I Backup of database 'database name' is bypassed because it is a secondary replica in an AlwaysOn Availability Group that is using Microsoft SQL Server Standard Edition.
Explanation
Backup processing bypasses the database on a secondary replica in an AlwaysOn Availability Group that is using Microsoft SQL Server Standard Edition.
System action
Backup processing continues but the database on a secondary replica in AAG that is using Microsoft SQL Server Standard Edition is skipped.
User response
Install SQL Server Enterprise Edition and retry the backup.