Hi
Do you have a six-channel soundcard on your edit Mac to monitor the surround audio correctly?
With one installed you change your FCP audio configuration to correctly output six seperate channels of audio. You can assign each audio stem track to a specified output channel.
If FCP is still set up in a two-channel stereo output mode then I suspect all your audio is being mixed-down by FCP to a stereo mix before output being passed to Compressor.
I assume you can set up the necessary FCP six-channel output configuration without a multi-channel sound card, but since I have one (a small Presonus Firebox, since its only needed for monitoring purposes) I’m not sure. But I guess that’s what you have to do.