The answer to 'why is my skylight leaking' is that there are several common causes, including improper installation, damaged seals or flashing, and general wear and tear over time. Symptoms of a leaking skylight can include water stains, mold or mildew growth, and water pooling around the skylight.
To fix a leaking skylight, you may need to reseal the skylight, replace damaged flashing, or in some cases, replace the entire skylight. While some minor skylight repairs can be done as a DIY project, it's generally best to call in a professional roofer, especially for more complex issues or if the skylight is high up and difficult to access safely.