Cubase LE5 and ZOOM R8, NO SOUND!

Hi, I’m using ZOOM R8 as a Interface for Cubase LE5. I can recording my song via microphone from it, but I can’t hear anything from headphone from ZOOM R8. I set up about device, VST, MIDI, then restarted my Mac, but nothing changed. ZOOM R8 works as a MTR, I can hear my recorded song from the headphone. I really don’t know why the headphone doesn’t work only use it for Cubase LE5. Please someone help me.