The checkout says "Sorry, the required quantity is not available. We are unable to deliver this product to this location"

Products are normally shipped from our distribution centres, and not from individual stores. If there is no stock available in the distribution centres, you will not be able to select We'll deliver it at checkout for the product.  

The product may have some stock left in stores for pickup only. Stores can not ship products.

You can check the stock availability from the product page, click here for how to do this.