by olifer.pt » Sun Dec 27, 2015 5:53 pm
I have tried and all the solutions worked. As soon as I remove the extended discount the promo code gets done.
When you remove the "extended" if the promo code is applied, even if it shows the invalid code message you may see in the order summary window that the discount has been made ( shipping = 4,99; promo code = - 4,99).
If the values are right, just ignore the message and proceed to checkout (it seems that the page does not refresh the error message at once.