A very weird apple bug and its fix - external displays becoming black making it unusable

date

Jul 27, 2025

slug

apple-display-turning-blank-bug

status

Published

tags

Tech issues

type

Post

old content?

summary

I encountered a dual monitor issue on my Mac due to a corrupted display configuration; deleting specific system preference files and rebooting fully resolved it.

Here’s your text, formatted in your writing style, with only minor rewording (within your 10–20% limit) and broken into clear sentences and paragraphs:

Strange Dual Monitor Issue on Mac

A few days ago, I ran into a really strange issue with my setup.

I use a dual monitor display. Out of nowhere, after some update (I’m not even sure which one), one of my external displays stopped working. At first, I thought it just wasn’t being detected. The screen was black. I tried swapping the HDMI cable, but that didn’t fix it.

For context, my setup is like this: I have one monitor connected via a Type-C hub, which also connects my keyboard and mouse. The other monitor is connected directly via HDMI. The problem was that one of these displays just wouldn’t show anything. It was being detected, but the screen stayed black. I couldn’t see it in the system info or in the display settings. That got me thinking—maybe this isn’t a hardware issue, but a software one.

So, I tried unplugging one display. By default, only the monitor connected via Type-C would work. The HDMI one was unusable. I tried disconnecting the HDMI, and the other display worked. But as soon as I connected both, the HDMI display would go black again.

I even tried swapping HDMI cables, but no luck. Eventually, I managed to fix it by moving the Type-C hub to a different port on my MacBook. My MacBook has three ports, and for some reason, the setup only worked with one specific port. Also, clamshell mode wasn’t working. I tried searching for an answer but couldn’t really describe the problem well, so I didn’t spend much time on it.

This issue kept bugging me for a while, but I never really gave it any time. So today, during my free time, I decided it was finally time to fix it. At first, I tried solving it with the help of ChatGPT, but I couldn’t find a solution—maybe because the AI didn’t have access to the latest data or because I was not able to provide all the context. I started by searching on my own, and then I dug deeper into Apple’s forums. Eventually, I found the exact issue. Here’s the link to the thread where it’s discussed:

macOS Sequoia 15.3 wont let me detect my … - Apple Community

Now my second display (thunderbolt) which worked perfectly, about 2 hours ago is now dead and cant be detected. I've looked on line and it turns out it's a common problem. I wish I had just left the upgradfe.

In short, the problem was that my display configuration was corrupted. As soon as I plugged my external displays into those specific ports, macOS would load that corrupted configuration, and one display would go blank. The answer in the thread suggested deleting those configuration files using a terminal command—there’s no graphical way to do this; I couldn’t find it in any YouTube video either.

Running the command from the link clears your display configuration settings. Once you reboot, everything starts fresh, and your displays work like new.

One thing I noticed in most answers online is that people weren’t checking the system configuration files. The real fix is to clear the display preferences from all the right locations, not just the user Library. The answer in that thread covers this.

Steps to Fix the Issue

1. Disconnect all external displays.

2. Run this command in the terminal:

3. Reboot your Mac.

That’s it. This fixed my display issue completely. One more day of encountering weird tech issue.