Speaker not turning on

Hello Together,

I've got used speaker. I've discovered that the battery was not there so I've ordered new one. New one arrived - I've measured DC - everything is fine with battery itself.

Usb-C charging - works. Around 0,5 A current during charging.

Unfortunately - there is no lights/no response to buttons.

What I've discovered is that I do not have 3,3 V on this small board which is connected via ribbon cable [the one with 2 buttons Blueetoth/Power and LEDs].

Voltage which is there is 0,8 V.

Where to look for problem? Do You have any idea?