Nord Lead 2x: no button operate on panel

[Chok1966]

Hello everyone
I bought a Nord Lead 2X but I have a problem, none of the panel buttons work so I can't switch to poly, try to switch back to factory presets. All the potentiometers work fine, it's just that all the panel buttons don't work.
Do you have any idea where this could be coming from? (I've checked all the power supplies and tested the 20-pin ribbon cable, everything's ok).

[maxpiano]

Hello, could be a loose flat cable inside, open the NL it and check all cables between panel and mainboard (unplug and replug on both sides, to be sure)