Welcome to the forums. It's possible, the ball retainer or the nut that the adjusting screw tightens in, might have fallen off inside the engine if you turned the adjusting screw too much. On the other hand, it might not be adjusted correctly.
The proper way to adjust is to loosen the locknut and turn the adjusting screw counterclockwise slowly, until you feel resistance. Then, turn the adjusting screw clockwise 1/4 turn. Now, hold the adjusting screw while you tighten down the locknut.
Note: If you've already turned the adjusting screw counterclockwise a lot, you may have to turn it back clockwise a few turns and then start over. My guess is that it's just out of adjustment, but if it won't adjust, something may have fallen out of place.