I'm trying to configure a Shopping Cart Price Rule to offer free shipping on matching items only (certain products). The rule works fine when I have none of the products in the cart (regular table rate shipping rates I have configured), or only the sale products in the cart (free shipping).
However, when I have any mix of products - the sale products PLUS some other non-sale products - a shipping method error displays (the text from Tables Rates > Displayed Error Message appears), and the user cannot check out.
Why is the table rates error message appearing? The behaviour I'm looking for is free shipping for the sale products, and regular shipping charged for any other products in the cart. Instead, the user cannot complete the checkout process if they have a sale and non-sale product in their cart at the same time.
I don't think it is because of cart rules, just disable rule and try if it occurring or not. if occurring again, check the configurations of Tables Rates.
It's because of the Shopping Cart rule. It only happens when the rule is enabled, and when a product subject to the conditions on the rule is also in the cart.