The answer to 'why is my shower no hot water' is that there are several common causes, including a broken water heater, a problem with the water heater thermostat, a leak in the plumbing, or a blocked showerhead. The symptoms you may notice include lukewarm or cold water coming from the shower, and the water heater not heating up properly.
Some potential solutions you can try yourself include checking the water heater thermostat, cleaning the showerhead, and inspecting the plumbing for any visible leaks. However, if the issue is with the water heater itself or requires more extensive plumbing work, it's best to call in a professional plumber to diagnose and fix the problem correctly.