The answer to 'shut-off valve won't flush' is that the shut-off valve may be stuck or malfunctioning, preventing proper water flow to the toilet. This can be caused by mineral buildup, corrosion, or mechanical issues with the valve itself.
Some common symptoms include difficulty turning the valve, water not shutting off completely, or the toilet not flushing properly. In many cases, the shut-off valve can be repaired or replaced to restore proper toilet function. However, if the issue is more complex, such as damage to the plumbing system, you may need to call in a professional plumber to diagnose and fix the problem.