Third-party calculated shipping rates(Carrier calculated shipping) must be required to use this app. And it’s not because we don’t want you to use the app without CCS but this is a restriction imposed by Shopify.
What is Carrier calculated shipping? If you want to display calculated rates with your own account or third-party apps at checkout. If you want to display your own shipping carrier rate on Shopify checkout then Make sure that your store has Carrier calculated shipping enabled.
In which plan are the Third-party calculated shipping rates supported? You need to have the carrier-calculated shipping feature on your store’s Shopify subscription plan to connect your own shipping carrier accounts to Shopify. This feature is included in the Advanced Shopify and Shopify Plus plans and can be added to any plan for a monthly fee. For more information, contact Shopify Support.
Above I attached a screenshot where it displays the “Third-party calculated shipping rates” which is only allowed on the “Advance plan” of Shopify. You can click here to get more details about the Shopify plans and their features.
What if you have a Basic or Shopify plan? It is not necessary to choose the advanced plan of the Shopify subscription but here are the different options to enable the “Third-party calculated shipping rates” on the “Basic Shopify” or “Shopify” Plan.
Once you choose one of these above options, after that you can use the custom shipping rate using our app on Shopify checkout.