m audio keystation 49e is recognized but not working

hey everyone the m audio keystation 49e is recognized by my macbook but it's not working. In garageband for example the volume slider moves the volume slider in garageband's mixer and changes the volume and if move the pitch bend and modulation wheel while playing through garageband's onscreen keyboard it changes the sound, but if i play any keys on the keystation nothing happens. Also when i plug it in a message pops up saying "The number of MIDI inputs has changed. Now one input is available." Can anyone help me out. Thanks