The answer to 'why is my fascia curling shingles' is that the fascia board, which is the horizontal board that runs along the roof's edge, is likely warping or curling due to moisture exposure. This can cause the shingles on the roof to lift and curl as well.
Common causes include poor ventilation, water damage, or simply age and weathering of the fascia material. Over time, exposure to the elements can cause the fascia to warp and twist, leading to issues with the shingles above it. If left unaddressed, this can lead to leaks, water damage, and further deterioration of the roofing system.