The answer to 'my flashing is failing' is that the flashing around your roof's edges or penetrations has likely become damaged or worn over time. This can cause leaks, water damage, and other roofing issues. Common causes include weathering, poor installation, or damage from extreme weather events. Symptoms may include visible cracks, holes, or gaps in the flashing, or signs of water intrusion like stains or mold.
In many cases, replacing the flashing is a job best left to professional roofers. Flashing installation requires specialized tools and techniques to ensure a proper, long-lasting seal. However, for minor flashing issues, some homeowners may be able to make simple repairs themselves, such as re-sealing gaps or replacing small sections of flashing. But it's important to carefully inspect the problem and determine if a DIY fix is appropriate or if you need to call in a roofing contractor.