[Q] Only vibrates - sc6820

Hello guys,
I have a Chinese android, sc6820 model.
I recently tried to root it but no success, on the contrary, just breaking it.

I was in fastboot mode, and tried the command: fastboot flash system "system.img".
It took a long time, so I canceled it (ctrl + c).
Now he does not care anymore, the only thing it does is vibrate (the screen does not light up, no sound).
When I plug in usb, appeared as "Unknown Device", but now no longer appears.

Model: Spreadtrum SC6820


Can anyone help me?

I will be very grateful to anyone who can help me.