The Audit Trail service needs to log in to your Laserfiche repository in order to retrieve audit logs.  The error indicates that the account you have set it up to use does not have the required permissions.  Either change the account you are using, or give that account rights via the Laserfiche administration tool.  I haven't reproduced the error myself, but the error message might be confusing in the case where you're using Windows authentication, because the user name that's passed around is blank - when it should really insert the process identity into the message.

After you straighten that out, you'll be able to tell Audit Trail what data to load into its reporting database.  If you indicate a date range like "the last 30 days", current data will be imported on a regular basis.