No need to say thanks bro..
I got this email in reply from Alienware:
Unfortunately, a key could not be assigned to you. This can occur for one of several reasons, including: 1) We've ran out of keys before we could assign one to you while you were in the queue. 2) You are in a country or region that is not eligible to receive a key. 3) A key has already been assigned to you. Please check back later as more codes may be added! Alienware Arena Team
Second is more like the reason I think..