A: Guitar Rig’s Rig Control requires a stereo connection to your computer audio interface, but it employs the left and right channels in a special way. The “left” channel carries your guitar signal, while the “right” channel is normally dedicated to control messages from the Rig Control unit’s pedals.
You may have plugged in Guitar Rig in Logic as a mono audio object and then switched the object to a stereo object. This won’t work. You must first create a stereo audio object, then plug in Guitar Rig. If done otherwise, after switching to stereo the plug-in will remain a mono input plug-in, as it was instantiated as such. Logic does not convert it to a stereo plug-in automatically. Therefore the plug-in will not be able to receive the input from Guitar Rig’s right output.