Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
I'm going to share what I understood when I had the same problem.
The Audit function of Microsoft Purview searches only activities executed by admins or other users delegated to the searched mailbox.
Activities runned by the owner aren't searched by this tool.
The only workaround found was using PowerShell:
New-MailboxAuditLogSearch -StartDate "YYYY-MM-DD" -EndDate "YYYY-MM-DD" -Mailboxes list-of-mailboxes -StatusMailRecipients email-address-of-who-needs-audit -LogonTypes Owner -Name "Custom audit name"
The biggest problem with this PowerShell command is that the result may arrive after days with an error message, without any data.
The Get-AuditSearchLog doesn't show the progress and this is disappointing.
I never found a valid solution to this.
PS: I have E5 + EMS E3