If your Carrier Service is not activated, please enable it on your shopify store.
Click on the link to enable Customer Carrier Shipping API on your shopify store and follow instructions as shown on the next steps
Click on your store Settings then select Shipping and Delivery
2. Scroll down and click on Connect carrier account
To activate the third-party carrier-calculated shipping, your store needs to be on the Advanced Shopify or Plus plan. If you're on the Shopify plan or lower, then you can add this feature for a monthly fee or switch from monthly to yearly billing.
Then contact Shopify Support for get this enabled (https://help.shopify.com/en/questions#/shop-select)
The Shopify Support Team will confirm once the third-party carrier-calculated shipping feature is enabled.
Option 1
Click on your store Settings
2. Select Shipping and Delivery > Shipping > General Shipping rates then click Manage
3. Select Shipping to and click on Carrier and app rates (1)
Option 2