I received a coupon in the mail to "Take $5.99 off your next Xfinity On Demand movie rental or purchase. Or simply use it as a credit towards your Xfinity bill." To redeem, it says to visit my.xfinity.com/coupon and follow the easy on-screen steps to activate the coupon. When I got to that site, I am asked for a 16 digit code to activate the coupon. The problem is there is no coupon code and my account is showing I have no credits. How do I go about this??