The answer to 'why is my shut-off valve clogged' is that the valve can become clogged due to mineral buildup, debris, or corrosion over time. This can restrict the flow of water and prevent the valve from opening and closing properly.
Some common symptoms of a clogged shut-off valve include difficulty turning the valve, water leaking around the valve, or no water flow when the valve is opened. In some cases, the valve may be completely stuck and unable to be turned at all.