Macbook Pro 16”s external display doesn’t work

I had a similar issue. i changed the resolution on my external monitor when the lid was closed to a level the monitor didn't support (not intentionally). There was no way that I could find to reset the resolution back to something supported (multiple questions here, none of the solutions worked for me - reset NVRAM, SMC, or key strokes with blank screen to change display preferences). I also tried use Automator to reset the display preferences, but couldn't get that to work with lid closed either.

Note that the external monitor was fine when the lid was open. However, changing display settings for the monitor with lid open did not persist when the lid was closed.

I eventually found a way to do it from the terminal command line:

1. Install screenresolution utility using Homebrew:

brew install screenresolution

2.Get the resolutions of the currently connected monitors:

screenresolution get
2020-09-05 13:47:12.444 screenresolution[3330:48127] starting screenresolution argv=screenresolution get
2020-09-05 13:47:12.470 screenresolution[3330:48127] Display 0: 1680x1050x32@0
2020-09-05 13:47:12.470 screenresolution[3330:48127] Display 1: 1920x1080x32@60

3.The external monitor is Display 1, so wrote the following command but did not press enter

screenresolution set 1920x1080x32@60

4.Close lid, wait for error to show on the monitor, then press enter on external keyboard.

After a second or so the display settings change took hold and I could use the monitor again.

Hope that helps someone. I couldn't find this specific solution anywhere else, but pieced it together from some other hints and tips.



I use MacPorts instead of HomeBrew, but sirosc's solution also worked for me.

$ port install screenresolution

$ screenresolution get
2020-10-13 18:56:45.495 screenresolution[844:17873] starting screenresolution argv=screenresolution get
2020-10-13 18:56:45.507 screenresolution[844:17873] Display 0: 1920x1080x32@60

Note that it's not showing the built-in display for some reason. I have no idea why. But I went ahead and followed the instructions: type the command but don't press enter, then close the clam shell and wait for the external monitor to display its "input not supported" message, and then pressed enter. A couple of seconds later, the external monitor started working.

$ screenresolution set 1920x1080x32@60

Thanks, sirosc, for posting this solution. This resolved a very annoying situation.

Edited to add: if you aren't using HomeBrew nor MacPorts, you can easily build the screenresolution utility from source. This is its github repo: https://github.com/jhford/screenresolution

When you choose [√] Mirror Displays, you force the internal and external displays to BOTH use a compromise resolution, so that they can both be run with the same display-generator. You need to un-check that box when you expect to close the lid soon, so that the display will not revert to unexpected (and possibly out-of-bounds) settings.

Once you uncouple the two displays, if you ever find that one display is out-of-bounds, you should be able to use the (Gather Windows) button to put all the Displays settings dialog boxes for all individual displays onto the active display, where you can adjust them on the displays you can see..

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If your LAST working display has its settings set to out-of-bounds, you can fix that with Safe Mode (hold shift at startup). Safe mode does a five-minute disk repair as it starts up, then demands your userid and login password, even if you normally auto-login.

Most extensions, including graphics acceleration, are not loaded. Screen updates will be wonky and slow and you may see the screen re-draw multiple times in slow motion. Defaults are taken for everything possible, INCLUDING screen settings, so you should have a default picture.

Settings you change in Safe Mode will "stick" in regular mode, so now is your chance to change the screen settings to something you can live with, and save the changes. Then when you restart into regular mode (which takes slightly longer [once]) your screen should use the last settings you made in Safe Mode..

Hi brijesh177,

Thanks for your post! We understand your external monitor will no longer function when you close the lid of your MacBook Pro. First, make sure you are using your device with closed-display mode enabled.

Use your Mac notebook computer in closed-display mode with an external display

If the issue persists, refer to the support article below for troubleshooting steps.

Get help with video issues on external displays connected to your Mac

If you notice the issue continues, see if the issue persists in another user.

Set up users, guests, and groups on Mac

Let us know what you find out!

Take care!

Safe mode didn't solve it. I was not mirroring displays. Changes to the external monitor settings made with the lid open did not persist when the lid was closed. When the lid was open i had display settings set for each display differently - as the command output above shows. Gathering windows didn't help either, because the bad settings were only in effect when the lid was closed.

What you are saying is baffling.

Except for mirror displays, I can't think of any way a different set of display settings could go into effect only when the lid closes.

It's helpful, thank you!