The answer to 'why is my shower frozen' is that your shower pipes have likely frozen due to extremely cold outdoor temperatures. This can happen when the pipes supplying water to your shower are located in an uninsulated or poorly insulated area, such as an exterior wall, attic, or crawl space. As temperatures drop, the water in the pipes can freeze, preventing water from flowing through the shower.
Some common symptoms of frozen shower pipes include no water coming out of the showerhead, the shower faucet being cold to the touch, and potentially visible ice buildup on the pipes. To resolve the issue, you'll need to thaw the frozen pipes as quickly as possible to restore water flow to the shower.