Icing Sheet is Dry & Brittle
This is mostly caused by dry conditions or if it was left open for a period of time and started to separate from the plastic or chip and crack.
Fill a container or pot with hot boiling water. Hold the sheet a distance from the steam for 1 to 2 minutes to soak up the steam. Don't do this for too long, it might become too moist. Alternatively you can place it in the refrigerator for a few minutes - also not too long.