If buyer doesn't reply for extend time is it become a late work?

[ruucreation]

Hi, I’m a new seller. But, these days I’m so busy with so much orders. So, I can not do a one order on time. So, I revised the order (Extend the delivery time) before the deadline. From now, within 3 hours my deadline is over. But, buyer didn’t respond still for it. So, I need to know if buyer didn’t respond before the deadline it becomes a late work? Hope your answers…