The answer to 'why is my skylight leaking' is that there are several common causes, including improperly sealed skylight flashing, damaged or deteriorated skylight seals, and issues with the skylight installation. Symptoms may include water stains, mold, or water dripping from the skylight.
To troubleshoot and fix a leaking skylight, first inspect the skylight for any visible damage or gaps around the edges. If the flashing is cracked or the seals are dried out, you may be able to reseal them yourself with caulk or sealant. However, if the issue is more complex, such as problems with the skylight installation or structural damage, it's best to call in a professional roofing contractor to assess and repair the problem.