This can happen if there is a blockage on the automatic sheet feeder (AF).
Check that there are no fragments of paper or sheets of paper, or staples, paperclips, etc. jammed inside the automatic feeder.
Also try cleaning the rubber rollers in the automatic sheet feeder.
Reply back and let me know if you get it working again.
If you need further assistance, please let me know the make and model number of the printer.