Let's remove, then install again.
Please press CTRL+D to bookmark this page, this way you can return after restart.
Click on Start, then Control Panel.
Click on Programs and Features or Uninstall a Program.
Scroll down to Kobo Desktop and Uninstall
Once it is uninstalled, please restart your computer.
Once your computer is restarted, please install Kobo Desktop again.
You can download it here. - http://www.kobo.com/desktop
Once you install it, please sign into it and let me know if it is working again.
If you have any questions, please reply and I will assist you.