Hey there,
there seems to be a problem in the coupon form ajax on checkout page with your theme.
when applying a coupon on checkout the the coupon doesnot appear in the totals / summary
right away afer applying and sometimes you get 403 error in the console.
most of the time, if you are refreshing you will see the coupon or if you will try to apply the coupon again you will see that the coupon is in the cart.
i have try to debug it in many ways:
1) try it on generic theme – twentytwelve – and the coupon work fine. you see right away in summary the coupon name and amout of discount
2) turn to the server to see if there is a problem or for some reason the server is blocking the request and there is no problem or blocking. they even try it on apache server.
that is why i guess it is a theme issue.
please help,
i will give you the staging address,
you can use this coupon: 20off
Amir