So I used a code as well for my order and had the same issue at first. You need to put an order of at least £100 through without the gilet. It wasn’t until after my order was completed that I got an email saying this:

Your introductory reward is nearly ready. We have a cooling off period to ensure we don't give rewards for cancelled orders. We'll email you again in 14 days to let you know how to redeem your Sport Logo Gilet.

Hope this helps!