Battery reading 0 V’s

[lorger]

Not sure if this is any help but I had a similar problem with display showing 0v but it was due to inadvertently pressing the red button when withdrawing the ignition key. This feature shuts down the (starter) battery to conserve power. It seems unlikely this would affect both starter and leisure batteries unless there was a quirk in the way the display was wired - assuming you have this feature of course. Mine is on a Peugeot Boxer.

Thanks for the reply, ours is a Fiat but will have a wee nosey anyway.