I have created a Shopify Development (Duties and Taxes preview) store because I'm creating an app that will calculate duties and taxes for international orders. The Shopify native checkout has a shipping step, where the products and shipping costs are totaled, with the shipping + duty and taxes combined into one shipping line. However, for Shopify Plus, I see the Duty and Taxes, can be separated from the Shipping value onto a separate line. I can see that Zonos have achieved this (https://cdn.shopify.com/app-store/listing_images/56e61599f63a9029bd4deb1d4a8793f8/desktop_screenshot...).
When I look at the Shopify REST Admin API; for the check-out, I can perform a 'GET' call, however, I'm unable to perform a 'PUT' call. When I try this is the error I'm getting.
"errors": "For access to web checkouts, contact support through your Partner Dashboard."
When I contact support, they keep referring me back to this forum community.
Please can you help me as to what I need to do to get access so I can add separate Duties + Taxes lines?