I'm having the same problem with my Kobo Forma, but in my case it refuses to connect in any port on either of two PC's, and I've tried all kinds of troubleshooting and done a factory reset. So I'm pretty sure I just have a bad USB port. It still charges, fortunately, but I can no longer sideload content. Anyway, hopefully someone will be able to help you resolve your own problem, since you know you can still connect on another computer; but if not you can always fall back on Dropbox, which is the only way I am able now to get most of my books onto my Kobo (although no kepub support):
https://help.kobo.com/hc/en-us/artic...r-with-Dropbox
Valuable lesson learned for me: my next ereader will
not be a Kobo or a Kindle, unless they once again start adding SD slots to their ereaders.
