The only way to get the credit according to their support is to pay with PayPal and then contact them with the order ID. They will then manually deduct the amount from the order. I too tried placing an order over a week ago with BTC after they first told me I had a credit and no credit was shown or applied on the order along with no coupon. I contacted their support again and they gave the pay with PayPal and contact them answer others have also received.