I've checked the process and there appears to be an issue in the the way the discount is applied. If you add an item to your cart prior to logging in, your code is not automatically applied.
I've got Mike looking into making the process more obvious. Meanwhile Willie I've refunded your $17.50 discount amount.
And since you're still a Gold Member until Mar 28 you can use your GOLDDISCOUNT code until them. (Actually, you haven't cancelled your membership at this point either, so if you do wish to cancel you'll need to revisit the MyMembership page).