Elements won't plug into my computer?

My WD Elements 2TB drive won’t plug into my ASUS Z87-A mother board. what’s up with that? It has 4 USB 3.0 ports, and 2 USB 2.0 ports on back but the Element won’t plug in to any of them. I thought USB 3.0 were backward compatible? I do have two USB ports on top of the case it will plug into, but I am using them for other things. Not sure what is going on.

What do you mean “won’t plug in”? Do you mean the connector doesn’t fit, or what?