The machine is out of paper or paper is not correctly loaded in the paper tray. Put the paper in the indicated paper tray. If the problem is not resolved, the paper pick-up roller may need to be cleaned. Clean the paper pick-up roller. (Click here to see the details of how to clean the paper pick-up roller.)
The paper tray indicated on the LCD is not installed properly. Re-install the paper tray that is indicated on the LCD.