Hello Solana,
Have you try resyncing the MCU keyboard with the NavNet 3D? To resync, while the unit is fully on press and hold the Left Arrow on the Scroll pad, Right Arrow on Cursor pad and Enter knob (Roto Key) until you hear 2 beep then you can let go. Also, just to double check make sure the MCU001 is connected to either Port 1 or Port 2 on the ethernet connection on the Black Box processor (MPU001).
YachtyBoy