I don’t think the knob is the problem, if it were it would just spin. I think something is jammed with the water level switch and that means buying a new one.
I found a solution, you don’t need to spend 100 bucks on a new water level switch.
Follow a video on how to remove the switch. Once you get it out, see if you can turn the knob while pressing down on the spring loaded cylinder (has a screw in the top). If you can, use a silicone based lubricant to coat the sides of the cylinder, and the notches on the red dial.