Midifighter 3d not working with ableton need help

I am running windows 7, ableton ver 9, midifighter 3d, midifighter utility newest update. i followed all the instructions on the setup guid it was working then stopped when i accidentally closed ableton mid song. My midifighter is recognished by the computer and the utility. i have made sure that the midifighter is set to the ableton setting. I have also uninstalled and reinstalled ableton. i have aslo factory resed my midifighter 3d several times. Still when i press a button on my midi using ableton no sound responds. my sound card is fine also. if i just press the play button on a sample in ableton a sound will come out. Pls help me. -Laurence