To log out of your Kobo account on a Kobo Clara BW, follow these step
- Go to your Home screen.
- Tap the More icon at the bottom of the screen.
- Tap Settings.
- Tap Accounts.
- Under the Kobo heading, tap Sign out.
- A confirmation screen will appear. Tap Sign out again to confirm.
Once signed out, the eReader will need to be set up again using a Wi-Fi connection or the Kobo Desktop app to log in.
A database corruption can happen with a perfectly working device. If could an improper eject. It could be the USB cable came out of the device before being ejected. It could be a problematic USB cable. Do the log out and log back in and that will recreate the database. After you've done this, setup Kobo Utilities in calibre to backup the database so if this ever happens, you can copy the last backed up database to your Kobo.