I placed two Costco gift card orders (one with my Amex and one with wife's Amex). Got a costco card in mail after three days. The second costco card (or the first one I don't know which one) never came in the post. Got fed up and called Costco. They refunded me the $100.
Now regarding the $25 cashback, I only got it on one order. Contacted Amex support and eMailed them proof of loaded card with offer(screenshot). Finally got $25 back.