When I try to backup O365 environment (Onedrive, MS Teams, Mailboxes and SharePoint) through Veeam backup server, I received the error that, Failed to find Team mailbox owner account and backup failed for the particular channel.
The detailed error is below,
Failed to process team: <example_channel> with Teams. Failed to find Team mailbox owner account.
I found this group <example_channel> is orphaned state, none is assigned as group owner. So I assigned one Global admin as owner to fix this.
Follow the steps to assign Group owner,
1. Sign in to the Microsoft 365 portal with an account that has administrator privileges.
2. Choose Groups from the navigation pane at the left hand side.
2. Search and find the group that you need to assign a new owner to and click on it.
3. In the new window appeared in right navigation, Select Owners tab, choose Edit.
4. In the View Owners dialog box, choose Add Owners.
5. Assign the right person(s) as owner and close the tab.
Note : Select minimum two recommended as by MicroSoft.