One of the more brilliantly worded Mac errors you may encounter is the curious “The application ‘Application.app’ is not open anymore.” message. This error is often seen when trying to interact with Preview, Finder, Steam, or many other apps either through one of the apps related files or through the app itself. Once you see the “Application not open anymore” error, the named app is basically inaccessible and unavailable and stuck open. Before you get overly concerned about what this means, we’ll show you a few ways to fix the “Application is not open anymore” error message in Mac OS.
The “Application is not open anymore” error is typically associated with the application in question becoming unresponsive and unusable, but it still remains shown as open in the Dock and often windows and associated items appear on screen still as if it is open. Nonetheless, Mac OS and Mac OS X think the app isn’t open despite the fact that it looks open, so in order to regain access to the application in question you’ll need to kill the associated app or process.
Fixing “Application is not open anymore” by Quitting the Associated Process
The simplest first troubleshooting trick is to simply force quit the Mac app that is mentioned in the dialog box. For example, if the app is “Preview” then you’d hit Command+Option+Escape and target the Preview app to force quit.
Sometimes you’ll discover the application mentioned in the dialog box is not included in the Force Quit Applications menu, which means you’ll need to rely on another method to force the app to exit. The next best approach is to use Activity Monitor, found in /Applications/Utilities/ and then narrow down the application name or associated process and kill the process directly.
Forcing the app or related process to quit is typically sufficient, and you should now be able to relaunch the application in question without seeing the “Application is not open anymore” error message. The app should open without a hitch, allowing you to go back to what you were doing with that application in question.
Rarely, rebooting the Mac is required to fix this issue, and typically that is only necessary if the application throwing the “application is not open anymore” message has many associated or child processes that are also stuck that you haven’t been able to successfully track down in Activity Monitor to force quit.
Why this happens isn’t entirely clear, but it appears that the application that claims to no longer be open, yet appears to be open, is simply stuck in some sort of crash or unresponsive loop.