This is likely a problem with
Android and
Windows having communication problems. This is a
known issue with recent
Android versions, and there is no fix yet.
A workaround exist. Another option is disconnecting the phone, rebooting, and reconnecting it.
This is nothing to do with KoBoSync, but is a general Android/Windows issue. Afterwards you should be able to go to the odk/instances folder and see the different subfolders for each of your interviews, allowing you to copy-paste them to your computer.
If you install a free file browser, such as
Astro or
ES, you can go directly to the instances folder on your tablet and you should see a number of subfolders, allowing you to verify that they are really where you'd expect them.
Hope this helps,