When I press the lower brightness key (F1) on my MacBook the screen turns off (pitch black). When I raise the brightness back (F2) everything is fine again. This only started happening recently with this machine and I can't think of anything that I've changed that could have caused this.

  • macOS Sierra 10.12.4
  • MacBook Pro (Retina, 13-inch, Mid 2014)

Restarting the computer resolved this. ¯_(ツ)_/¯

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  • Restarting my computer also worked – Natalie Davis Nov 13 '17 at 2:24

The first thing I would try is resetting your NVRAM.

Resetting the NVRAM

Older Macs had what's called Parameter RAM (PRAM), newer Macs use Non-Volatile Random-Access Memory (NVRAM). Here’s how to reset the NVRAM on your model:

  1. Shut down your machine. Yes, a full shut down, not just logging out.
  2. Press the power button and then press the commandoptionpr keys. You have to make sure you press these keys before the gray screen appears or it won’t work.
  3. Hold those keys down until your Mac reboots again and you here the startup chime.
  4. Let go of the keys and let your Mac reboot normally.

Note: When you log back in you may need to readjust some of your system preferences (e.g. speaker volume, screen resolution, startup disk selection, time zone information, etc).

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