Shipping script only runs when there are multiple items in cart

[KolbySisk]

I'm writing a script that will apply free shipping if the cart contains a specific item and a discount code is used. Here is my script

if Input.cart.discount_code && Input.cart.discount_code.code == "FREEITEM"
  ELIGIBLE_SERVICE = "Standard Ground Shipping"
  ELIGIBLE_ITEM = "424492626116"
  
  Input.cart.line_items.each do |line_item|
    if line_item.variant.product.id == ELIGIBLE_ITEM
      Input.shipping_rates.each do |shipping_rate|
        if shipping_rate.name == ELIGIBLE_SERVICES
          shipping_rate.apply_discount(shipping_rate.price, message: "Free shipping for this product!")
        end
      end
    end
  end
end

Output.shipping_rates = Input.shipping_rates

However, it only runs when there are multiple items in the cart. It should work when the specific item is added, even if it's the only item added.

[achieveapplabs]

Hi @KolbySisk ,

Did you select "line_item" as the type of script in Script Editor? Also at which point do you apply the discount because without a discount the remainder of the code would have never executed. 

Best,

Sam