Brick Amazon Kindle PaperWhite DP75SDI

[saudagi70]

Good morning, I have an Amazon Kindle PaperWhite DP75SDI that is probably blocked. Left on a book page. When I try to turn it off by holding the off button, the backlight turns off and then comes back on. I tried any reset, charged the battery to the maximum, but nothing worked. I connected via serial (cp2102) to the PC, I opened Putty, I tried sending when the kindle reaches uboot>, but if I try to send the bist, or fastvboot command, it remains blocked and nothing happens. What am I doing wrong? thanks so much!