The Office 365 Backup Health Report includes information about all Office 365 applications in the environment and indicates whether those applications meet the backup health requirements needed for backup operations. An entity (such as a mailbox, user, or other) meets the backup health requirements if the entity was backed up in the last 3 days.
Information in the report includes the number of entities that are backed up and not backed up. You can use this report to view the backup health status of each entity on each client computer in the environment, identify any backup failures for specific mailboxes, users, or other entities, and also determine what caused the failure.
You can use the Office 365 Backup Health Report to help maintain the environment, as follows:
Go to the Office 365 Backup Health report and view data for the last 3 days because that is the most critical time period.
If you see that the number of Associated Entities and Entities Backed-up tiles display the same number, then your backups are running perfectly, and there is no need for concern.
If you see that the value is greater than 0 in the Entities Not Backed-up or Entities Never Backed-up tiles, then you should see the Entities Not Backed-up table to learn more.
In the Clients Table Entities table, if any entities (such as mailboxes and users) appear in the Not Backed-up and Never Backed-up columns, see the Entities Not Backed-up table to learn more.
In the Entities Not Backed-up table, in the Backup Status column, configure a filter to display only Failed entities.
In the Entities Not Backed-up table, review the information in the Failure Reason column.
You can try to fix some errors on your own. For more information, see Troubleshooting Using the Office 365 Backup Health Report.
If you encounter an error that you cannot resolve on your own, open a support ticket.