GV125 Aquila Speedometer not working

Hi All,

Joined up on behalf of my nephew who has bought a 2016 GV125 and asked me to prep it for an MoT.  Aside from needing a front brake calliper, all seems well save for a non-functioning speedometer.  Seems to be an electronic type rather than a cable.  What goes wrong with these and how easy is it to fix without shelling out for a new dash assembly?

Thanks in advance.