instrument tracks have a strange attitude; they just won't behave i.e. from all things you're used to doing with MIDI and audio tracks, some of them just don't work with instrument tracks. I had the same happening with the VS-700 control surface (some issue were fixed, some still don't behave) ... try switching direct monitor on/off from the MCU for instrument tracks, many times it won't work.

bottomline, if the rec buttons don't light up (and they also don't do it in a new project which you just created with the latest Sonar version), pls put in a problem report. cake still got some work to do on the MCU as well as on instrument tracks