Remove Shipping on specific cards

Hello,

Since I am trying to contact you for almost 3 weeks in a row and no response from the website form. I am trying to get support by this channel. We are a paying subscription and would get atleast get some support.

We would like to know how we can remove the shipping cost when specific gift cards are entered. Not all cards, but specific ones. Is there a way we can check it with checkboxes what ones that need to remove the shipping cost?

We did find this code (https://www.pimwick.com/pw-faq/prevent-gift-cards-from-counting-towards-the-free-shipping-amount/) but that code is not working.

Thanks in advance!