oreo1912,
You'll have to take the bottom off of the machine and soak the entire lever and all it's moving parts in oil. Better yet Tri-Flow.
The latches are controlled by a flat piece of metal that slides in and out of the latches. Follow it with your eyes and soak those latches.
From the top you might have to use a small screwdriver and gently coax the latches up as you work the lever, then work the plate out. It's easier to do this if you remove the needle, presser foot and rotate the hand wheel till the feed dogs are at their lowest position.
The latches are a hollow tube with a spring loaded plunger inside them. They can get stuck bad and with the plate in you can't get any oil into the plungers from the top. And not much from the bottom. That's why you've got to work the plate out.
Joe