You should be using the "Reports" tab. Set the Start date to something way in the past (e.g. Jan 1st, 2012) and that way it will always pick up anything older. Make sure the "Reported" Filter is set to "No". After you have run the report and confirmed you got it ok, then it asks you to mark as Reported. That way you will not miss anything. If you use the optional Invoice module, you will used the "Invoiced" filter instead.
