What is the actual error from calibre? It probably means that it is a corrupt database and needs to replaced. This can be done on the newer devices by signing out of the Kobo accounts. I'm not sure how to do that on the WiFi.
Otherwise, it sounds like
https://www.mobileread.com/forums/sho...d.php?t=221072. And the solution is to restore an image to the internal SD card.