Please make sure that:
- you have selected your MIDI device in menu File > Audio and MIDI Settings > MIDI Devices > Port A, B, C or D (standalone mode only).
- you have enabled Record for your instrument/MIDI track in your preferred DAW (plug-in use only) – e.g. here is how the record button looks when enabled in Pro Tools.
- you have selected the correct MIDI Port and Channel in your Part.
- you are playing notes in the valid range.
- you are not triggering notes from a multi-out preset that is routed to separate plug-in outputs.