The answer to 'why is my shut-off valve no hot water' is that the shut-off valve may be faulty or turned off, preventing hot water from reaching your taps. This is a common plumbing issue that can have several potential causes, including a stuck or broken valve, mineral buildup, or a problem with the water heater.
If the shut-off valve is turned off, simply turn it back on. However, if the valve is stuck or broken, you may need to replace it. This is a relatively simple DIY task for most homeowners, but if you're not comfortable working with plumbing, it's best to call a professional plumber to handle the repair.