Hello, I’m Nathan, and I’ll be assisting you today. My livelihood depends on your positive feedback, so your satisfaction is my highest priority.
Sorry to hear you’re having trouble.
This indicates a defect in the duplexer unit which could be as simple as a jam or debris, though there are many possible failure points including a faulty feed/drive system or bad logic board.You can remove the duplexer from the back side, blow it out with compressed air, and clean all the rollers/wheels with rubbing alcohol and qtips.
Reassemble and let me the results.