I have a new Ecosys p5026cdw printer, and when I try to select duplex printing, I can make the selection, but when I print, it's back to single-sided. I go to the Windows Control Panel, then select 'Devices and Printers', then the 5026cdw and right-click to get to 'Printing Preferences', then 'Basic' then 'Duplex: flip on long side' and click on 'OK'. At that point, it SHOULD print on both sides of the paper, but I still get single-sided. Any clues?