- So, you’ve downloaded and installed a new Mac app, only for it to refuse to open. Now, you’ve got to work out whether it’s a problem with macOS, an incompatibility issue, or even a security threat. Let’s try to solve the problem and launch that app.
- Close Other Apps That Could Be Using The Camera Or Microphone. It’s possible that Zoom is not working on your Mac because the Camera or Microphone (or both) are in use in different app. Before joining a Zoom meeting, close any other apps that might be using the Camera or Microphone. This includes apps like FaceTime, Skype, and Photo Booth.
Mac App Store and identified developers: When you try to open a new app and it’s not on the list of identified developers that’s saved within the operating system, the Mac tells you it can’t.
To quit (close) a Mac app normally, choose Quit from the app's menu in the menu bar, or press Command (⌘)-Q. If the app doesn't quit, follow these steps to force the app to quit.
How to force an app to quit
Press these three keys together: Option, Command, and Esc (Escape). Or choose Force Quit from the Apple menu in the upper-left corner of your screen. (This is similar to pressing Control-Alt-Delete on a PC.)
Video playback mac app. Then select the app in the Force Quit window and click Force Quit. Avira security mac app.
https://hbkdlrl.weebly.com/blog/trello-app-download-mac. You can even force the Finder to quit, if it stops responding: Select Finder in the Force Quit window, then click Relaunch.
Learn more
App Cannot Be Opened Mac
How to force an app to close on your iPhone, iPad, or iPod touch.