You can enable Pritnful's live shipping rates for Ecwid Business and Unlimited plans by checking this box:
If you're sellingitems that are not fulfilled through Printful, we recommend disabling the live shipping rates. Since these live rates only show shipping costs for Printful products, you're likely to lose profit if items that are not fulfilled by Printful are added to the cart.
Your customer has added 2 items to the cart:
A product fulfilled by Printful
A product fulfilled by another service
Only live shipping rates for the Printful product will be calculated and displayed, while the other product won't be factored into the shipping costs. This essentially means that you're offering free shipping for the other product.