If you do not use the printer often, the paper may have been in the paper tray too long. Turn over the stack of paper in the paper tray. Also, fan the paper stack and then rotate the paper 180° in the paper tray.
Try to follow these steps:
Open the back cover.
Push the gray lever to the right as shown below.
Close the back cover and re-send the print job.
When you have finished printing, open the back cover and reset the lever back to the original position.