Shopify doesn’t currently support custom error messages to display through ShipperHQ; however, you can change the default error message through the Shopify platform itself.
- From your store admin, head to Settings > Checkout
- Scroll to the Checkout Language section and press “Manage Checkout Language”
- Scroll down to the Checkout Shipping section.
- Edit the text in the “No rates for cart or destination notice” textbox.
Test your error message in the cart/checkout.