The applied epoxy has been over recommended curing time and why did it still not cure and remain sticky?

There are various reasons of not curing such as low temperature, off-ratio mixing, insufficient mixing, high humidity, lack of ventilation, incorrect resin or hardener. Please note that epoxy hardner is not catalyzt. Adding more hardener do not make it cured faster. Only follow the proper mixing ratio with proper temperature and ventilation is the key for curing. For proper mixing ratio and temperature, please refer to the product catalogue for detail.