Single knob moen shower spins without any change in water. The screw inside the knob cap can control the flow of water with a screwdriver but will not unscrew to remove the knob. The knob has no affect on water and just spins. Any input on how to resolve this. Thanks

Replace knob. May have to break off knob to hold cartridge to remove screw. Maybe not. This a clear acrilic knob, right?

It is clear acrylic. Under the knob cap there is the screw with a washer then the knob. Thought that I would have to break it. Thanks kindly for your info.

Place screwdriver between knob and wall, pry knob away from wall while trying to unscrew screw. Knobs already broken in center maybe this will grab stem. No luck, push knob toward wall, tap gently but firmly with hammer. May be able to break out center completely. No luck, pry it off with hammer claw. Most you could do is damage little retaining clip around cartridge. Its replacable. Turn water off or you are going to get wet.

Shut the water off. Pull the handle out and grasp the strem with a pair of needle nosed pliers. You may now unscrew the stem screw and remove the handle. Replkace with a Moen replacement handle. Good luck, Tom

Thx to all the input everything went well and is working now. Thank you.