The answer to 'why is my skylight missing shingles' is that the shingles around the skylight have likely become damaged or worn over time, causing them to detach from the roof. This can happen due to factors like sun exposure, high winds, or improper installation. Without the shingles, the skylight opening is left exposed, which can lead to leaks and further damage to the roof.
To fix this issue, you'll need to inspect the area around the skylight and replace any missing or damaged shingles. This may be a relatively simple DIY project if the damage is minor, but if the underlying roof structure is also compromised, it's best to call in a professional roofing contractor to assess the full extent of the problem and make the necessary repairs.