I have not been able to solve this. I am currently using Shopify’s Debut theme. I had a Shopify expert help me but they did not get it working. All they did was place all of the github code in the cart-template.liquid
When the button is pressed, it displays “Calculating…” but returns without results and the button text reads “Calculate Shipping” again.
Also it might be helpful to note that I am using a shipping calculator app called Intuitive Shipping. I was also using Advanced Shipping Rules prior and with both shipping apps the calculator would not work.