Kenmore Water Level

My dishes have not been coming out clean from my Kenmore Dishwasher (model # 587.15152400). I think the problem may be with the water level. As far as I can tell the, water only level barely fills up the very bottom of the dishwasher, as shown with in the yellow line. I think the water level sensor is marked in red, but the water doesn’t even come close to this.

Would this problem be an issue of a bad water sensor, or something else?? My concern with the water sensor is that the water is not even getting close to it, so how would it sense the water level?? Hos does the washer know to stop entering water if the water sensor does not tell it to stop? Any ideas or suggestions?? Thanks!

I’m not sure how to edit my post above, so I wanted to add that the check ball had been removed sometime ago by a “professional” repair person saying he has seen these balls be an issue to the washer.. could the lack of the ball be attributed in any way to the above issue?? Thanks!