Shopify has changed how carrier-calculated shipping (CCS) is activated on their plans.
Access to CCS is NOT available on the Basic Plan (Paid yearly or Monthly)
There are 3 ways to activate CCS:
1. Subscribing to the "Shopify Plan" for a full year
2. Subscribing to the "Shopify Plan" monthly + an extra $20/month for CCS
3. Subscribing to the Shopify Advance Plan