@Murohy: Have you
a) checked that the computer itself is seeing the Kobo (if it can't calibe can't).
b) ensured that the Kobo device interface plugin in calibre is not disabled?
You could do as the post
My device is not detected by calibre says and capture the debug log and share it; from that it is easy to tell if the interface is disabled and if the device is being seen by Windows,