Shopify Checkout UI For Custom Shipping Carrier

I’m creating a custom carrier to use our delivery rate ,
I’m able to see the custom carrier in Carrier and app rates tab
also when I call the API to get the list of carrier , the

callback_url is correct .
But when we try to test in checkout page, it is not loading our carrier.
it is not even calling our API, we don’t have any log to a call in our server.

https://quickstart-16fda700.myshopify.com/checkouts/cn/Z2NwLXVzLWVhc3QxOjAxSFY3M0dBREFLM1lWTkNDRzBRVkNOODhG