OKI MB 461+LP Blank screen suddenly

[rapidocument]

Hello guys,

OKI MB461+LP Model,

the customer brought this machine for poor quality
but while in the shop I noticed that the screen goes blank
all of a sudden and won't respond to any button until you turn it off.

D o you know if there's any service bulletin on this? or if you have an idea
on whats going on,

Thanks,