The only thing I see might be the minimum order value of MX$599.00, as your order is exactly MX$599.00. Have you tried adding more products to it or lower your minimum order value (with, let's say, 1 cent). Did you also check if there hasn't been a discount already on the product? As it can't be combined with automatically added discounts.
Another thing could be that the address is not in Mexico, but that seems unlikely.