My car has recently developed a fault where there is no audio (radio or bluetooth). It's not on mute and if you turn the volume up then you can see the scrollers going up and down. Columbus system....anyone know how to do a hard reboot or any suggestions?

Ignore - fixed it by doing a soft reset (hold down the on/off button on the screen for 10/15 seconds)

Mine does this occasionally but ONLY when streaming music from my phone via Bluetooth. So when I have it connected, then disconnected and connected again (like when you switch off and on quickly) there is a small chance to develop this. I can scroll up and down but no sound comes from my  phone even though I have started playback. I resolve this by switching sources a couple of times or turning off and on BT on my phone. However what I describe is more of a "Bluetooth brainfart" though, happens for example between my phone and the BT speaker at home occasionally.

If for example you have no sound from Radio or the SD then it's something else.