Press the Allow All button to allow the product to be sold at all times. This button is used for clearing the screen, making all of the boxes Blue, so that you can select a few times to prohibit selling of the product by clicking in the boxes.

To select all of the times, click on Select All (Highlighted in Red). Then click in the boxes to allow selling of the product. A red box signifies the product cannot be sold, and a blue box designates that the product can be purchased during that time.