External Monitor Issue After macOS Sequoia 15.1.1 Update

I had a similar issue this morning after updating to Sequoia 15.7.1. The external display was not recognized anymore after starting the Macbook M4. With my other Macbook everything worked fine, so I could almost exclude any hardware and cable issues.

What solved the problem was to go into the last Time Machine Backup and copy the file "com.apple.windowserver.displays.plist" from Time Machine backup in ~/Library/Prefences and paste it into ~/Library/Prefences on the Mac HD.

After re starting the MacBook the external display was recognized and is working fine again.

15.2. is available !

I just installed it on my MacMini and MacBook Air, returned to my previous adapter: the bug has been fixed obviously!

Hi again,

Updated to 15.2 and seems that the problem is solved now. Connected with Apple HDMI Adaptar in one USB-C and Charger in another USB-C.

Regards.

I have the same issue. The workaround is to power the monitor first with its own power supply and then connect the video (usbc or hdmi). Power and video delivery over 1 usbc cable seems broken.

Exact same issue for me as OP. After updating to Sequoia 15.2 (I don't recall what the previous version was), the flickering issue occurred immediately after the update. Nothing else has changed about my set up after the update, so I feel very confident that the 15.2 update is the root of the issue.

Here's my set up prior to Sequoia 15.2 Update:

• Macbook M1 Max, 16-inch, 2021
• MacOS Sequoia 15 (not sure which previous version)
• External displays:
  • Working normally: "Display 1", LG 27GN650-B (connected via HDMI port)
  • Malfunctioning, flickering: "Display 2", LG 34UM69G-B (connected via usb-c port, USB-C to USB-C display cable)

Steps that failed to resolve issue:

• Follow steps 1-4 outlined here. Did not resolve issue.
  • Unplug cable and monitor power cord
  • Mac is already at latest update
  • Restart Mac
  • Change color profile of external monitor to Color LCD
  • Change refresh rate to 60 hz
  • Disabled true tone/night mode where applicable
• Changed USB-C cables, and tried plugging USB-c cable into different USB-c ports. Neither resolved issue
• Swapped display cable from USB-c/USB-c to USB-c/DisplayPort. Did not resolve issue.

Steps that resolved the issue so far as of Dec 19, 2024 at 11:06:

• Swap display cables between Display 1 (working) and Display 2 (malfunctioning):
  • Display 2 is now connected via HDMI cable to mac HDMI port
    • Color profile: Color LCD, 60 Hz refresh rate, no true tone/night
  • Connect Display 1 via DisplayPort to USB-C mac port

Since swapping display cables between external monitors, the flickering has stopped. I will update accordingly if anything changes.

If someone gets a problem with second (and third) monitor not being recognized by MacOS after Sequoia 15.2 update you might want to check this link on reddit. TL;DR: you might need to remove /Library/Preferences/com.apple.windowserver.displays.plist file and restart to make it work again. Now Apple, pls solve this issue officially.

I've the same problem on my MacMini M1 with two LG 34" monitors. One of them, connected by an USB-C/Thunderbolt to HDMI adapter cable, gets dark for 1-2 seconds every few minutes since updating to 15.1.1.

When I changed the refresh rate to 30 Hz, then BOTH monitors showed this behaviour, surprisingly simultaneously!

Another USB-C to DVI to HDMI adapter chain didn't help. Looking for some other hardware in my junk box, I found an adapter box for VGA, DVI and HDMI. Using HDMI again, both monitors are as functional as before.

This solution worked for me.

Rather than deleting it, renaming the file to "com.apple.windowserver.displays.plist" to "_com.apple.windowserver.displays.plist" works as well. After you rename it, restart your mac, and your mac should detect your display now.

Macbook Pro M1 Pro, running Sequioa 15.4, using USB-C to Display port via thunderbolt dock, and a LG 27UD68 display.

Ordered a new docking station/KVM for my Mac Air M2 and now all is back to normal. I run with an external mouse, keyboard, camera, and monitor and close the Mac up to switch between work Windows laptop and my personal mac. I don't know that there are any DisplayLink updates in the 15.1.1 update but my issue started about that time. Or, seeing as how the older docking station didn't have any sort of heat sink and just ran blazing hot all the time, it may have just been on its last legs. Regardless, haven't had any issues since using the new docking station so I'm happy now. If you're interested, here's the link to what I got on Amazon:

https://a.co/d/c8BC06S

There are a lot of these things out there, but this had just enough USB ports and the one HDMI port. No more issues for me. Hope this helps.

Janusromanus wrote:

This is incredible!!

I updated to 15.2 and the issue dissapeared for almost 4 days, and now it happens again.... how is this possible?, I contacted apple and they told me they dont have notifications about similar issue regarding Sequoia....

I suspect this is more of a corner case for them, given the amount of activity I see on this and similar threads. So they don't really care. I haven't been actively gathering data, but does this look like it's only happening with older external hardware? My monitor certainly is old and I've no intention to changing it, for sure not because of poor drivers from Apple...

I will uninstall Sequoia and will try Sonoma.

I've been back on Sonoma for 7 days now and even installed a security update. I've been fine so far, issue seems to be gone.

I have a Samsung monitor with max refresh rate 144hz. What worked for me was reducing the refresh rate of the monitor from 144hz to 120hz.

I accidentally fixed my issue. I shut down and restarted in safe mode. The external monitor seemed to work using USB-C. So I shut down and restarted. And now it works fine. I didn't change anything or do anything differently. Just the safe mode restart. I am not sure if this is a fix, but it worked!

Solution for me (Problem solved):

macOS 15.3:

I bought a new USB-C to HDMI cable and now it's all fine! Connected directly to the Macbook's USBC port, no hub.

No screen failure, no "blackouts" for three full working days.

I don't know if this works for everyone, but it is worth a try.

I took my refresh rate on internal monitor from ProMotion to 60 Hz but it failed to fix it.

I took my refresh rate on internal monitor from 60 Hz to 50Hz and IT FIXED IT

Tks Faiz!

Tried everything else on this thread with no success only to get to the end and see this suggestion to reset the monitor to factory defaults, worked immediately!

Thank you, you are a hero!