Chuwi HI13 doesn't boot

Hello, I have a problem with my Hi 13. It doesn’t start.
I followed this guide How to install Ubuntu on a CHUWI HI13: How to install Kubuntu on a Chuwi Hi13
When I went to install screen, it began splashing and now I can’t turn it on. Red led doesn’t light neither when I plug charger nor when I press start button, even though power led on keyboard does. I’m sure that battery is not a problem, I charged it to 7.4V directly and no change. When I plug charger and measure voltage it drops a few volts and battery starts draining. What could be the problem?