DIAGNOSIS: You're getting a false jam alert. This is almost always a tiny piece of torn paper or a paper dust sensor trigger in the rear paper feed area, which is a blind spot.
FIX: Clear the rear feed path. Power off and unplug the printer. Open the rear cover (the flimsy plastic door at the back). Shine a flashlight inside and use tweezers to gently pull out any debris or a paper sliver you see. Manually rotate the white rollers with your fingers to check for anything wrapped around them. Close the cover, plug in, and power on.
IF THAT DIDN'T WORK: The error might be a faulty sensor. Perform a full reset: with the printer on, hold the Stop (red X) button for 10 seconds until all the lights flash once. This clears the error memory.
HEADS UP: Never yank jammed paper backwards; always follow the arrow direction printed inside the guides to avoid tearing and leaving the fragment that causes this.