The answer to 'why is my sink frozen' is that your sink's plumbing has likely frozen due to cold temperatures. This is a common problem during the winter months, especially in areas with freezing weather. When water in the pipes freezes, it can cause the pipes to expand and block the flow of water to your sink.
Some common symptoms of a frozen sink include no water coming out of the faucet, slow or irregular water flow, or gurgling noises coming from the drain. In some cases, you may also notice frost or ice buildup around the pipes under the sink.