search-MailboxAuditLog is empty - Mailbox Audit Logging not working in Exchange 2013 CU6 environment

Hello,

i activated Mailbox Audit Logging for Admin, delegate and owner with all supported operations (update, delete, etc..)

like mentioned here: http://exchangeserverpro.com/using-exchange-server-2013-mailbox-audit-logging/

But also two days later (and also one Server reboot later) search-MailboxAuditLog is still empty.

any ideas how to fix this?

Best,

martin