Remote pairing

I have a bit of an odd problem I am hoping someone caan help me with. I just bought an apple remote. I tried pairing it with my Mac Mini by holding down the menu and FF buttons for six seconds but I never get the pairing symbols. If I go into Security Settings the button still says Pair instead of Unpair, indicating that it is not paired. And yet the remote works. Kind of. If I clipck Menu, Plex starts snd I can navigate. I can wake the computer with the remote but I can't put it to sleep m

What am I missing?

Mac Mini 2011. Latest Mountain Lion.

Thanks.