PicassoTab tablet won't turn on

Hello

I have a PicassoTab (standalone drawing tablet). For the past few months, the tablet shuts down as soon as it is not plugged into a power source. If I try to turn it back on, it lights up before turning off again a few seconds later, regardless of the available charge.

When it is plugged in, there is no problem using it. But I would really like to be able to draw somewhere other than in front of my power strip.