The charger is in hot/cold delay mode. The battery pack is outside its safe operating temperature range.
Remove the battery pack from the charger. Let it sit in a room-temperature environment (approx. 65-75°F / 18-24°C) for several hours. Do not attempt to charge a hot or freezing cold battery. The charger is designed to delay charging until the battery reaches a safe temperature.
IF THAT DIDN'T WORK: The battery pack may be defective or damaged. Inspect for cracks, swelling, or leakage. Under abusive conditions, liquid can be ejected. If the pack is damaged, do not use it. Take it to an authorized service center.