The answer to 'why is my water heater frozen' is that your water heater is likely frozen due to extremely cold temperatures or a malfunctioning heating element. This can happen when the temperature around the water heater drops below freezing, causing the water inside to freeze and expand. This can damage the tank and other components.
Some common symptoms of a frozen water heater include no hot water, strange noises coming from the unit, and the tank feeling cold to the touch. To fix a frozen water heater, you'll need to thaw it out safely, which may involve turning off power, draining the tank, and using a space heater or other method to slowly warm the unit. If the damage is severe, you may need to replace the entire water heater.