The answer to 'my shingle replacement is failing' is that there are several common causes, including improper installation, weathering and age, and damage from storms or other external factors. Symptoms can include curling, cracking, or missing shingles, leaks, and increased energy costs. The solution often requires full shingle replacement by a professional roofing contractor.
Shingle replacement is generally not a DIY project due to the risks of working on a roof and the need for specialized tools and skills. Trying to DIY can lead to further damage and safety issues. It's best to call in a licensed and insured roofing contractor to properly inspect the roof, identify the root cause, and complete the necessary repairs or full replacement.