When using iTrack Solo or Scarlett solo with Keynote on Mac, there appears to be a peculiarity with how Keynote manages its inputs. Because of this, these particular interfaces appear to only record on the left side of the stereo spectrum.

As a workaround, you can try forcing OSX to output your system sound in mono via System Preferences > Accessibility > Audio > Play stereo audio as mono.  

Please ensure you change this option back when using other DAWs that are fully supported.