Razer Leviathan Mini won't turn on.

Hello.
My Razer Leviathan Mini won't turn on.
At first I was thinking it's a battery problem, but I disassembled the speaker, unplug the battery (it's was 7.26V) and charge it with LiPo Balancer charger to 8.4V. Plug it back to speaker but the problem is still there.

If I push the button, the BT LED made a short-short blink, PW LED doing nothing. If I plug in charger (5V 2A) PW LED pulsing red, as it should in charging mode. But have no any reaction on PW button.

I have no any Service Center near my house, so was thinking try to repair it by myself.
Maybe you could give me any advices what should I check? Visually the PCB's have no any burn SMD's, the capacitors also looks good.

I would ask for datasheet, but hardly anyone will give it to me. So just ask an advice.

*If someone's needs any photos from inside, PCB's etc. or advices how-to-open-it I'm ready to share.