Thank you for reaching out. I am sorry to hear you are having technical issues with your shipping. This can be tricky to solve as many things can create this issue. I will list the most common things that can cause this, and you should be able to get it resolved quickly!
Please double-check your shipping rates to make sure they are set up correctly for each location and a rate for all prices/weight an order can be. You can locate your shipping rates by going to Settings > Shipping in your admin.
Ensure products are not marked as "no shipping required" in their product details. You can find this by going to Products and clicking on a product to see the details.
Check that all shipping locations are enabled, and keep in mind which locations you have inventory in, as that location must have shipping enabled.
Make sure you have a default package set up to calculate your shipping rates.
If you have gone through these steps and are still receiving the error message when trying to checkout, don't hesitate to reach out to our Support Team for additional help. You can contact our Support Team by email, live chat, or callback request through our Help Center. You will need to log in, select your shop, search a topic, then click "Continue" at the bottom of the page to find contact options.
Please let me know if you have any further questions!
Emily | Social Care @ Shopify - Was my reply helpful? Click Like to let me know! - Was your question answered? Mark it as an Accepted Solution - To learn more visit the Shopify Help Center or the Shopify Blog