These are possible solutions. Try one or more of the following:
Check the paper size and type to make sure the paper is supported by the printer. If you are using automatic duplexing, use only letter- or A4-size plain paper.
Check for and clear any paper jams. For more information, see Paper jam in the duplex unit.
Remove the duplex unit and reinstall it. For more information, see Paper jam in the duplex unit.