This error occurs when the paper in the tray is not the correct size and is not available for automatic 2-sided printing.

Press (Cancel) or Cancel. (if required)
Load the correct size of paper in the tray and set the tray for that paper size. Select a paper size supported by 2-sided printing.

Paper sizes available for automatic 2-sided printing are A4^*, Letter^*, Legal^*, Mexico Legal^* and Folio^*.
 

*: Letter, Legal, Mexico Legal and Folio for USA/ Canada/ Latin America, and A4 for others.