If the PanelDue powers up - ie displays something don't make the mistake I made and press the buttons on the panel and erase the firmware. If you do it's fairly easy to upload the firmware using Bossa and the USB connector.
https://duet3d.dozuki.com/Wiki/Connecting_an_LCD_control_panel#Section_Connecting_a_PanelDue
After I had the screen displaying information it sat on a screen saying connecting. I changed out the cable for a 2nd one, still had the same issue. Turned out a poor crimp on the connectors that failed only when plugged in. Very annoying fault.