It's not a simple uninstall/reinstall. There are some extra folders that you have to delete. I had a similar issue. Reader Library would show the Menu Bar at the top of my desktop and the process running in the dock but no window with the program. I uninstalled and reinstalled following the suggestions in this link, including changing the language references in System Preferences to US Computer.
https://www.mobileread.com/forums/showthread.php?t=78921
I have since learned that perhaps there is a simpler solution. Before you uninstall/reinstall, I would try to delete the kinoma files per this link, specifically Post #8:
https://www.mobileread.com/forums/showthread.php?t=59980