The offer input body should include cart data that adheres to the following criteria. The merchandiseTotal should be the sum of all cart items, minus all discounts, plus the shipppingAmount. The totalAmount should be the merchandiseTotal plus the taxAmount. If you update the cart data for testing, please be sure that it conforms to these standards.
A capture request typically has the merchandiseAmount, which should be the same as the totalAmount minus the taxAmount. If you updated the cart data, please update this to match the merchandiseAmount.