Make sure "Stack" mode is disabled. This mode allows you connect several XV5080's via MIDI thru ports and manage heavy polyphony issues by telling each XV5080 to only respond to certain notes. Of course, this is NOT what you want if you only have one XV5080 (or if they're not specifically configured as a "stack").

To check "Stack" mode:
1. Press SYSTEM
2. Press F3 "MIDI"
3. Move the cursor to select STACK
4. Make sure MODE = OFF