When connecting an audio device to your Mac, there are two reasons why Ecamm Live may not pick up all of the device's audio channels.
Most input devices can take advantage of Ecamm Live's Echo Cancellation feature to reduce echo and background noise. Note however that when Echo Cancellation is turned on, only channel 1 of an audio device will be used. All other channels will be ignored. If you need channels other than channel 1, turn off Echo Cancellation by unchecking the checkbox in Ecamm Live's Sound Levels window.
Ecamm Live's Audio preferences include a checkbox called Map Input Channels 1 and 2 To Left and Right Stereo. If this checkbox is checked, Ecamm Live will only use channels 1 and 2. All other channels will be ignored. When this checkbox is unchecked, Ecamm Live will mix all input channels together.