We've divided all the viable solutions into two parts for your better selection. You need to kill the associated app or process in order to regain the access to the application by applying some advanced methods. Even if you do manage to close the app, then it'll usually refuse to disappear completely, for example, it may remain visible in your Dock, or pieces of the app will appear onscreen at random. Typically, once you've encountered this error the application in question will become unresponsive and you'll be unable to close and relaunch it using normal methods. That's weird because sometimes the named application is actually open and it's onscreen at the moment, the error still arises. It's more like a stubborn error that you can never remove it permanently. When users are trying to interact with applications like Preview, Finder, App Store, Safari, Google Chrome, Xcode, Steam, iTunes etc, a curious error message would show up 'The application xx.app is not open anymore'.
MacOS (Sierra, High Sierra) and MacOS X (Yosemite, El Capitan) expose one system bug in common. How do you solve the constantly showing up error 'The application is not open anymore'?
