What color is the motion tween you are using?
When I right-clicked in the timeline and created the motion tween it appears as a blue shade.
When I moved the ball down to the bottom of the screen, the motion tween line appearing on the stage appears as a green line with many edit points on it.
- Add frames to the tween after the keyframe where the ball is at the bottom.
- Click the last frame of that.
- On the stage, drag the ball up and adjust its shape as needed by scaling
I tried your instructions and it worked perfectly.