I also need help and I don't see any answers to Nathans' question which is somewhat similar to mine.
I can hear my piano through my headphones, but it there is no sound registering in Studio One. I have a Yamaha P515 piano. I am connecting it with a TRS audio cable ( both ends are TRS - its a standard instrument cable) from the AUX out L/R port via the PreSonus Audiobox2 to Studio One in my Toshiba laptop. I have added it as an external device in Studio inputting from the Audiobox2. I also have a microphone hooked up to the audiobox 2 and I am able to check my sound levels pre-recording and successfully record through that, but not the audio cable.
