PRAM RESET
Shut down your Mac, then turn it on and immediately press and hold these four keys together: Option, Command, P, and R. You can release the keys after about 20 seconds, during which your Mac might appear to restart.
- On Mac computers that play a startup "chime", you can release the keys after you hear the startup "chime" two times.
- On Mac computers newer than 2016, you can release the keys after the Apple logo appears and disappears two times.
SMC RESET
- Shut down your Mac.
- On your built-in keyboard, press and hold all of these keys:
- Shift
on the left side of your keyboard
- Control
on the left side of your keyboard
- Option (Alt)
on the left side of your keyboard
- Shift
- While holding all three keys, press and hold the power button as well.
- Keep holding all four keys for 10 seconds.
- Release all keys, then press the power button to turn on your Mac.