I have a Kobo Clara HD and one day it wouldn't connect to USB anymore. Changed cables, took it apart to examine the connector (it was fine), tried it on both my Desktop and my laptop, etc. I was about to give up on it when I found out that it just doesn't work with USB 3. Verified that by successfully connecting to an old PC downstairs on USB 2. Turns out I hadn't used the Kobo in a while and I had replaced my Desktop and ancient laptop since. Both those older machines were connecting on USB 2 ports.

Got a USB expander dongle on AliExpress for something like six bucks that breaks out a few USB 2 ports and the Kobo is happy as a clam. So am I now, because the Kobo is great.