Likewise, before you uninstall 5KPlayer on Mac, be sure to completely quit the app. Now you should have no problem uninstalling. If you receive the “5KPlayer is running” alert message after you click Uninstall in the Uninstall 5KPlayer dialog box, then please open Task Manger, right-click on 5KPlayer and select End task.
To uninstall 5KPlayer on Windows, make sure that you quit the app first.