Vu+ Genuine Universal Remote Control
Suitable for Vu+ Duo, Vu+ Solo, Vu+ Uno, Vu+ Ultimo, Vu+ Solo2, Vu+ Duo2, Vu+ Solo-SE, Vu+ Zero.
Configuring Remote to work on your Vu+ model.
Mode 0001 : Solo / Duo.
Mode 0002 : Uno / Ultimo / Solo2 / Duo2 / Solo-SE / Zero.
Mode 0003 0004: Reserved for future models.
1. Press and hold keys 2 and 7 together for three seconds until LED is on.
2. Press HELP
3. Enter 0001 or 0002 or 0003 or 0004 on remote keypad depending on the correct mode number for your model receiver.
I think the Duo switched to Mode 0002 at some point.
So try the instructions above and see if it works.