Hmm :/ I assume you double checked your power connections, if not do that. That's about all I got, sorry
But someone more knowledgeable may be able to help you out further.
I know this probably is the last thing you want to hear but you could also try contacting Asus and see if you can get it replaced. There is a 2% chance that you happened upon a defective product.
Also, regardless of how much or how little you may know about building a computer, I'd recommend watching the 3 part series of how to build a computer that I linked above (at least the 2nd part), it contains just about everything you need to know about building a computer.