@lucylucy: DO NOT FORMAT the card. That error comes from the fact that Windows does not properly handle removable with multiple partitions. If you have formatted it, the way to recover is with an image.
If you haven't formatted the card, you might be able to recover with a manual factory reset. Follow the last set of instructions on
https://wiki.mobileread.com/wiki/Kobo_Reset:_Glo_HD.
Otherwise, you need an image. There are instructions for doing this at
Memory Upgrade Mod Guide. They are for the Glo, but the basic steps and tools are the same.
But, to get the image, you need to enable Private Messaging. This is in the "Edit Options" of the control panel. If this isn't there, it has to be added somehow. You can try posting in
https://www.mobileread.com/forums/sh...d.php?t=319819 to ask for it to be enabled, or contact a moderator.