If your Mac is using a firmware password, it ignores this key combination or starts up from macOS Recovery. If your Mac is using a firmware password, you're prompted to enter the password. macOS Recovery installs different versions of macOS, depending on the key combination you use. If your Mac is using a firmware password, you're prompted to enter the password.
Or use Option-Command-R or Shift-Option-Command-R to start up from macOS Recovery over the internet. Command (⌘)-R: Start up from the built-in macOS Recovery system.Keep holding until the described behavior occurs. To use any of these key combinations, press and hold the keys immediately after pressing the power button to turn on your Mac, or after your Mac begins to restart.
