With the risk to repeat myself (as I've posted also in the main thread for debricking the kindle), as that thread took another direction and nobody answers my question, I will post here my problem again.
Si dear moderators, please forgive me for this, I really do not want to flood the thread.
So, my problem is, my uncle has tried to update duokan on his kindle, and some reason it got stuck at the loading screen. I've suggested him to enter the debugging mode by holding the 'enter' key (it's a kindle wifi) and from there, to mount the USB and try to copy to duokkan files again, or delete them. Unfortunately, due to ingonrance, he has pressed button 'I' which has formatted the partiitons.
Now the kindle is here, and I wanted to debrick it.
First, I've downladed the rescut kernel and rootfs, compiled k3flasher under linux, and restored the kenrel and rootfs. From this point , after switching power, the green led does not turn on any more, and the kindle does not boot either. Also, the MAC and serial number has been erased, it looks like.
Then I've create da backup from my identical working kindle, and tried to flash all the files, except the rootfs. They completed without error, but the kindle seems dead also. The screen doesn't change at all, and I cannot even enter the debug screen.
Any help would be appreciated. The kindle is alive, as I can flash with k3flasher any time I want.