Q: cant get motif XF8 to work with logic 9

I cannot get my motif XF8 to work with Logic 9, nor is it working with any other DAW.  I have used the motif since last summer and it has always been hit or miss with MIDI.  Sometimes it works, other times it doesn't.  The cord is connected appropriately. I am mystified, and embarrassed to admit that I really don't get MIDI at all.  I have a  Macbook pro that is a year old or so.  Please help.