You may want to try either a manual factory reset or enabling Developer mode (in the search box, type devmodeon and then search). You should then see in
More =>
Settings =>
Device information =>
Developer options. Under
Developer options near of the bottom of the entries, you will find
Factory reset your eReader.
Here's the link for the
Manual reset Kobo Libra Colour procedure.
Either of these will wipe your Kobo back to the factory firmware version removing all user information.