Look into the Developer's Corner. This might be fixable with the
https://www.mobileread.com/forums/sho...d.php?t=230158 approach.
But writing an image of a working internal uSD card to a replacement uSD card may be your best chance. You can get a larger internal memory that way as well.
https://www.mobileread.com/forums/sho...d.php?t=209122
Luck;
Ken