Ipod synch problem

bought an album of music from the apple store uploaded ti to my Ipad no problem

however when trying to sync it to my Ipod followng message appears

Saturday night jump could not be copied to the ipod because you are not authorised for it on this computer.

the rest of the songs are on the ipod.

how do i get this one song to sync ???

via iLounge Forums http://ift.tt/1wIk1Kb