Problem solved : unit reverted to normal after a complete cycle of 24 jours "clicking".
And Vinnie Rossi has been fast and responsive, with the answer :
It sounds like it was dropped in shipping and one of the relays on the SMART board is in the incorrect state. These are "latching" relays and being subjected to dropping can cause them to change state.
Luckily - there is a way to handle this. If your customer uses a hammer and taps the right side of the enclosure (using sufficient force), that should get the relay to go back to the correct position, and then the unit should turn on. He should do this when he hears the "clicking sounds" when he tries to turn it on.
I also recommend he uses something like a piece of wood between the hammer and enclosure so he does not scratch the enclosure. But he needs to tap it fairly hard to reset the relay.
All the best,
Red Wine Audio"
In fact, no tapping required : it just did some reset of its own and works flawlessly now.
I have to laugh at a manufacturer actually telling the customer to hit the product with a hammer. But hey, Vinnie knows what he's talking about.