I had that problem on Windows 10 with my Glo HD. Here is the solution.
Download and install the Kobo desktop app (
https://www.kobo.com/desktop).
Launch the app.
Plugin your Kobo device. It should now mount without issue and show up on the Kobo app.
Launch Calibre.
It should recognize your Kobo device.
When you're done eject the device not through windows nor Calibre but through the Kobo app.
This problem has happened to many people that upgraded (as opposed to clean install) to Windows 10. It's not specific to the anniversary update which I have not done yet.
Also I have not had any problems with my Aura H2O, go figure.