Black screen after changing display resolution on Mac mini with BenQ monitor

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Black screen after changing display resolution on Mac mini with BenQ monitor

I have lost the use of the monitor hooked up to my Mac mini and Apple Support doesn't know what's wrong.

I have a Mac mini (M1, 2020) plugged into, via an HDMI cable, a BenQ monitor (BenQ XR Series EX3501R 35" 3440 x 1440 Resolution 100Hz DisplayPort, 2x HDMI, USB-C HDR10 FreeSync Flicker-Free Low Blue Light Ultrawide LED Backlit Curved Gaming Monitor).

Everything was fine for years until I decided to change the *display resolution* in System Settings. The screen immediately went black and a pop-up message said that no signal was detected. I have been unable to get it back.

The twist? Each one of these three items still works well.

I can hook up my BenQ monitor to my MacBook Air and use it to either mirror or extend my screen.
The very same HDMI cable works fine when plugged into the MacBook Air and my BenQ monitor.
I can now use my Mac mini by plugging it to a loaner Acer monitor from a friend of mine.

I've tried restarting my computer multiple times; using a different HDMI cable; plugging the cable to the other HDMI port on my monitor; changing the display resolution while I have the Acer plugged in and switching back to the BenQ. Nothing works. It looks like a communication problem between my Mac mini and my BenQ monitor and I can't get the original resolution so that the monitor turns back on again.

Does anyone have any idea how to fix this very silly and confusing problem?

[Re-Titled by Moderator]

Original Title: Strange problem: changing display resolution made my screen go black... and I can't get it back

Posted on Jul 15, 2025 06:23 PM

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Answer 1

Jul 15, 2025 07:13 PM in response to jjarry

I'm thinking that the Mac is remembering the last resolution you used with that monitor. Every time that it is trying to be "helpful" by restoring that resolution, it is re-creating the problem.

If you can hook up the BenQ monitor to your Mac mini's HDMI port, and hook up the Acer loaner monitor to one of your Mac mini's rear-panel USB-C ports at the same time, you might be able to reset the "resolution" that the Mac uses with the BenQ directly, from Displays Settings.

--------------------

As for where the Mac is remembering the resolution, my guess is

~/Library/Preferences/ByHost/com.apple.windowserver.displays.LONG_HEXADECIMAL_STRING.plist

where the value of LONG_HEXADECIMAL_STRING might be different on your system than on mine. I used Xcode to look in my Mac's version of that file, and one of the entries there had fields whose values corresponded to what I'm using in Displays Settings.

Possibly if you removed that file and then rebooted the Mac, the Mac would regenerate it minus the troublesome setting.

You could remove the file either by going into Terminal and typing

rm ~/Library/Preferences/ByHost/com.apple.windowserver.displays.*.plist

or by selecting Option-Go > Library in Finder, opening the Preferences folder, opening the ByHost folder within it, and dragging the file to the Trash.

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Answer 2

jjarry Author

Level 1

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Jul 16, 2025 06:51 AM in response to den.thed

Funnily enough, I tried this. The black screen with the limited options *does* show up on my BenQ monitor (another proof that the screen itself is fine). But when I hold down SHIFT to boot my hard drive in safe mode, the screen goes back to black. No signal detected.

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Answer 3

den.thed

Level 10

88,756 points

Jul 16, 2025 07:18 AM in response to jjarry

The Shift key at startup only works for Intel Mac's.

Start up your Mac in safe mode - Apple Support

You need to follow the Safe Mode directions for a Silicon Mac.

Shut down your Mac.
Press and hold the power button on your Mac to turn on your Mac and load startup options. When you see the startup options window, release the power button.
Select your startup disk. It's named Macintosh HD, unless you changed its name.
Press and hold the Shift key, then click the “Continue in Safe Mode” button below your startup disk.

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Answer 4

jjarry Author

Level 1

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Jul 16, 2025 05:36 PM in response to Servant of Cats

Thank you so much! Your instructions were clear and they allowed me to solve the issue. While the Acer monitor didn't have a USB port, I did manage to connect both monitors at once and sure enough, the BenQ was working just fine.

I had to unplug it and only plug in the Acer loaner monitor; manually delete the file you pointed out in the Library; shut down the computer; unplug the Acer and plug in the BenQ; and restart the computer.

Back to normal.

You saved me from a really frustrating headache. Thank you!

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Answer 5

den.thed

Level 10

88,756 points

Jul 15, 2025 07:01 PM in response to jjarry

Startup in Safe Mode followed by a normal Restart.

see > Start up your Mac in safe mode - Apple Support

Also see > If your external display is dark or low resolution - Apple Support

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