This probably belongs in the Getting Started section. Having said that, you're likely doing it wrong. You record a mono source to a mono audio track and a stereo source to a stereo audio track. Of course, to record a stereo signal(of any kind) it takes 2 inputs/preamps. What exactly is your guitar source that you are referring to as "stereo"? If it actually is stereo(like the output of a Line 6 Helix), then you need to take 2 signals(left and right) from that source and connect them to 2 inputs of your interface. Then create a stereo audio track and select the proper PAIR of inputs. If that pair appears to not be available, open Setup>IO and select the INPUT tab and see what input paths are showing. It might be as simple as hitting the DEFAULT button, or adding the proper path manually(maybe watch some youtube tutorials on how to customize the IO setup). If this doesn't help, come back with complete details on everything and every connection
