-I went to http://www.amd4u.com/radeonrewards/splash.
-I clicked Redeem my Coupon Code.
-Entered my details(Step 1. Please fill in the form below for your AMD4U account).
-Entered my code(Step 2. Please enter your 12 digit unique coupon code*)
-And then the error appears.
Note: I didn't select any game... Didn't had the option.