If, when using a computer, you find you are not able to hear 8 notes being played, it may be that duplicate notes that are sent from ARGON8X's keyboard, then echoed (or 'MIDI Looped') back to it's external USB or DIN MIDI ports.
This situation can arise when connected to a computer and a DAW or sequencing software package (Ableton Live, Logic etc.) has the ARGON8X as the currently selected destination for MIDI data.
One solution to this is to turn ARGON8X's 'Local' control to 'Off' ('Settings - UI & Controls' / Keyboard / Local). This prevents MIDI notes from the internal keyboard being received by the internal voice engine and only transmitted via MIDI.