While the Admin Console runs, it creates an admin_console.lock file to prevent multiple instances from launching. Closing the window using the X button or selecting Exit from the File menu removes the lock file automatically.
However, closing the command prompt or terminal directly leaves the lock file in place. If you try to start the Admin Console again, the command prompt will display:
Application is already running. Please close the existing instance first.
To continue, go to the folder and manually delete the admin_console.lock file.