ERR0227 : the product discount shouldn't be more than the line price including existing product discounts.
If you see this error while trying to refund a Walmart order, this is Walmart's message saying, "You are trying to refund more money than what the order was for."
Here are a couple possibilities for the above error message.
A. The amount you are setting for the refund is higher than what the order is. Double check your numbers to ensure you are using the correct amount!
B. The refund has already been processed, and there is no further action required on your end. You should be able to double check the order in your Walmart Seller Center to confirm that it is indeed refunded!