The answer to 'my fascia is failing' is that the fascia board, which is the horizontal board that runs along the lower edge of your roof, is likely deteriorating. Common causes include water damage, rot, insects, or general aging and weathering over time. Symptoms may include cracks, warping, or the board pulling away from the roof structure.
To address a failing fascia, you'll need to inspect the damage and determine if it can be repaired or if the entire board needs to be replaced. Minor cracks or warping may be fixable with wood filler and paint, but more extensive damage will likely require replacing the fascia board. This is a task that is generally best left to a professional roofing contractor, as it involves working at heights and ensuring the structural integrity of your roof system.