MacBook Pro displays Apple Logo and Prohibitory Symbol My  MacBook Pro 15" displays the  Prohibitory Symbol on start-up. What can I do to fix it?
The Apple website mentions what a prohibitory symbol means:


  Prohibitory symbol
  
  
  A circle with a line or slash through it means that the selected startup disk contains a Mac operating system, but it's not a macOS that your Mac can use. You should reinstall macOS on that disk.