If your Capture software is giving you an error message about being in "Stereo Mode," my suggestion is to take a look at the below knowledge base article that explains this.
What does "Cannot create new sessions if the audio device is Stereo," mean?
This link will tell you everything you need to know about making sure you are selecting the proper driver, and making sure your mixer is connected and functioning correctly over the digital source you are connected to (i.e. Firewire).