The answer to 'pressure regulator no hot water' is that a faulty pressure regulator is the most common cause. A pressure regulator controls the water pressure entering your home, and if it's not working properly, it can reduce or eliminate the hot water flow.
Some common symptoms of a bad pressure regulator include low water pressure, no hot water, and water that fluctuates between hot and cold. This is typically a DIY-friendly repair, but if you're not comfortable working on plumbing, it's best to call a professional plumber to diagnose and fix the issue.