We allow only one coupon to be used per order. If you have more than one code, you might be able to use your other code sometime in the future if you want to make an additional order with us. But each order only allows for one code.
If you'd like to redeem a promo code on your order, all you need to do is add the code into the provided text box within the checkout process on the CART page before you submit your order to us. Please note that all coupon codes must be added before completing the checkout process, and we're unable to provide codes of any kind on PayPal payments, or in cases where a Bitcoin discount is being claimed. Keep in mind that a code cannot be added to your order once it is submitted, so be sure that your code shows up in your order summary before you select the 'Place your order' button.
If you think there is a glitch in the use of your discount code please contact us and we will do the best we can to help you out.