The answer to 'why is my gutter guards curling shingles' is that improperly installed gutter guards can put excessive pressure on the shingles, causing them to curl and lift. This can happen when the guards are too tight against the roof or when they are screwed directly into the shingles instead of the roof deck.
Gutter guards should be installed with a slight gap between the shingles and the guards to allow for proper airflow and expansion. Screws should be anchored into the roof deck, not the shingles themselves. Improper installation can also trap moisture under the guards, leading to rot and mold growth that can further damage the shingles.