Usually get that kinda promo code from attending a GIE or New England grows or one of the other shows, promos only good for a period during and right after the show, something you would have gotten by visiting the booth at the show, you’re looking at the website where there is a slot for it, but that’s why, it’s only good for show season.
Just buy the thing, no one has a code in their drawer sitting there that would be good unless it’s right after a show... and there aren’t any I know of this time of year