No Audio when recording a keyboard or synth.

[ringjamin]

HI I am using a Allan & Heath Zed R16 mixing/firewire desk with a macbook pro running logic 9. When I record voice or guitar with an microphone, logic will record it and I can subsequently play it back and here the recoding through my head phones (head phone are plugged into the mixer) . However, when I record my keyboard or synth through the Allan & Heath mixer, logic will display the audio wave image as if it has been recorded but when I try to listen back to the recording there is no audio ? This only happens when I record the keyboard or synth. Would it be a problem with in logic or with the mixer ? Any help would be appreciated regards.