Mailbox doesn't auto achive

we are using EV 9.0.4 installed on Windows 2003 x64

the user has configured his vault to archive a folder every 0day  from (outlook plug-in)

items located in the mentioned folder are archived if one of the following is true :

-  manual archiving by the user

- an admin force the archiving process through exchange archiving task > schedule >> run  now against this specific mailbox

If  the archiving task is left to run on its own schedule, nothing is archived.

We have already checked, dtrace and event viewer but we couldn’t find something wrong.

Also we have already zapped the mailbox and moved it to another DB  on the same server but nothing changed

Have any one faced this issue before?

Thanks in advance