DIAGNOSIS The paper sensor (a small plastic lever or optical sensor inside the rear feed area) is stuck, dirty, or broken, so it never detects paper.
FIX Clean the paper feed area and sensor.
- Remove all paper from the tray.
- Turn the printer OFF and unplug it.
- Open the rear cover. Use a flashlight to look for a small plastic lever or a clear window (optical sensor) near where paper first enters. Blow out dust with canned air.
- For a mechanical lever, gently move it up and down with your finger to ensure it springs back freely. Wipe it with a dry cloth.
- Reload paper, ensuring it's under the rear guide flap and the stack height is below the tray's max line.
IF THAT DIDN'T WORK The sensor itself may have failed. A common workaround is to use rear feed slot for every print job instead of the tray, as it uses a different sensor.
HEADS UP Overfilling the paper tray or using paper that's too thick/curled can physically bend or break the paper sensor lever. Don't force paper in.