What version of calibre are you using?
Could you run calibre in debug mode and post the logfile after connecting the Kobo.
On the Kobo website, goto My Account / My Books
https://www.kobo.com/ca/en/library?filter=Books
Underneath each book I see a menu of ... Selecting that gives me an option to download, which in turn gives me an ACSM file that has to be opened by ADE to provide an Epub.
Alternatively, you can use OBOK (part of the NoDRM plugin) that will retrieve a kepub format book from the Kobo desktop program.
Update: See
https://help.kobo.com/hc/en-us/artic...-device-or-app
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