[BRLTTY] HumanWare/Braillant question

[Shérab]

Dear all,

I am trying to use a Brailliant 40 after a long time of inactivity.
It's now more than two hours that the device has been plugged to power.
When the power button is pressed for one or two seconds, the beep
indicating that the device is on can be heard, but the braille display
itself does not seem to start, the dots remain in their intermediate
position. If the power button is pressed again, one can hear the two
beeps indicating that the device is turned off.

So it seems the whole device can be turned on, but the braille display
itself and the keyboard do not wake up.

Has somebody already met this problem?

Can I expect that leaving the device in charge longer will ultimately
resurect it or does it look like there is a deeper problem?

Many thanks in advance,

Shérab.