Oki ES3640MFP Service & Troubleshooting Manual page 84

Close the cover - Slide the paper guide to the center - Return cover to the original position.
While lifting MP tray, insert the white lever in the arm that supports MP tray, and lock it by lowering the white lever. (Both sides)
Move the paper guide outward, close the paper supporter, and close the MP tray.
Frequent Jams: Check if there is a piece of paper or foreign substance in the IN2 sensor. Check if IN2 sensor moves up
and down smoothly.