sampling from tables threw mpc to mac?

Hey,
Ive just changed from my old pc and bought this macbook and i am having troubles with recording samples. I have it all set up the same as i did with the pc when i plug in headphones to the mpc i can hear the record play but when i go to sample rec it dosent come threw with any audio. Any help would be appreciated

What are yours in and out set to in the RENs preferences?