The answer to 'why is my fascia curling shingles' is that the fascia board, which is the horizontal board that runs along the edge of the roof, is likely warping or curling due to exposure to the elements. This can cause the shingles attached to the fascia to curl and become loose.
Common causes of fascia curling include moisture damage, UV exposure, and improper installation or maintenance. Symptoms include visible curling or warping of the fascia board, as well as shingles that are lifting or coming loose. The best solution is to have a professional roofing contractor inspect the fascia and replace any damaged boards, then properly re-attach the shingles to prevent further issues.