Guohong, welcome to MobileRead!
If you've already tried everything advised here then it's difficult to recommend you anything else. Do I understand it right that you contacted Bookeen's support team? Do you still have warranty? Is it a possibility to send the device to Paris for repair or replacement?
And have you, by chance, seen this thread?
https://www.mobileread.com/forums/sho...d.php?t=122183
Part of it is in German, if you don't understand it, please ask again, I will translate it then.