title: Why is iOS Simulator not running?
body: <p>When I try to run my program, iOS Simulator goes black and displays this error:</p>
  
  <p><img src="https://i.stack.imgur.com/XvbHO.png" alt="Unable to boot the iOS Simulator"></p>
  
  <p><code>Unable to boot the iOS Simulator.</code></p>
  
  <p>When I click OK, Xcode shows this error:</p>
  
  <p><img src="https://i.stack.imgur.com/v8Lmp.png" alt="Unable to run app in Simulator. An error was encountered during running (Domain = NSMachErrorDomain, Code = -300)"></p>
  
  <p><code>Unable to run app in Simulator. An error was encountered while running (Domain = NSMachErrorDomain, Code = -300)</code> </p>
  
  <p>How I can I make it run again?</p>