External Monitor Issue After macOS Sequoia 15.1.1 Update

I have a similar issue. The external monitor that used to work fine prior to the update to macOS Sequoia 15.1.1 (LG 29UM69G), now flickers, i.e. goes off for about 2 seconds, then it goes back on. Happens on both my Macbook Pro M1 2021 and Mac Mini M1 2020. If I disable 'Prevent automatic sleeping when the display is off' in System settings, then my Macbook Pro goes to sleep when the flicker happens, ending any calls in the process.

This is completely random, it can work well for hours, or flicker every minute or so. I've been unable to link it to anything I do or have on my system.

Tried to change cables (USB-C, DisplayPort, HDMI), ports, screen refresh, and color profile to no avail.

Have USB-C dock connected. Worked fine yesterday, now it's working as by described others. I switch back and forth between my work Windows laptop and my personal Mac Air M2. Works fine on Windows laptop but not on Mac Air 2. Is there a way to go back to previous version of Sequoia or is there a fix coming anytime soon?

Same problem as all the others. WIsh now I hadn't updated. Other things have changed and quit working as well but this is the most important one for me. I use two monitors in addition to my laptop. This is for business - not for games. When will Apple respond? Better be soon or I will stop heralding Mac's value to everyone I know! Shame on you Apple for not doing your job properly. Not the kind of quality I have experienced over the last 25 years of Apple ownership!

Same issue for me the moment my MacBook Pro update to 15.1.1. LG monitor flickers and comes on for a second then black screen. Worked flawlessly up until now and I've tested several other monitors with the same results. since I use an external monitor for work all the time. Seems like this would be a massive widespread problem. Hope this gets noticed and fixed asap!!

[Edited by Moderator]

Same problem here. Sequoia 15.2. Went straight to Sequoia 15.2 from Sonoma, which was working fine.

Three Dell U3223QE displays connected to M1 Max Mac Studio, all via USB-C to USB-C. Two of the displays are fine. The third exhibits the problem described here. Sometimes the screen goes black every few minutes. Sometimes it's stable for many hours. Windows never move positions and it is always restored within a few seconds. Not a showstopper, but definitely a consistent workflow annoyance.

Come on!!!!!!! This is SO frustrating.

• I've tried all suggestions, nothing works! Details of the issue:
• 14-inch Macbook Pro M1 2021 (Macbook 18,3) on Sequoia 15.2 no longer recognizes external display (Brand: HGFRTEE) that worked just fine on Sonoma.
• Using USB-C ports. Have tried all ports, none work with this monitor; all of them work with another monitor; the monitor works fine in all USB-C ports when using my other 14-inch Macbook Pro M1 2021 (Macbook 18,3) on Sequoia 15.2 (identical model and version).
• For some reason, my Macbook recognizes the display instead as a sound output, named DPAudio.
• The monitor doesn't say "No signal detected"; instead, it shows a black image, but the Macbook doesn't detect the display. Alt + Detect displays does nothing.

When are we getting a fix? This is just awful!!!

Same issue here too. Macbook Air M1.

External Pen display, Huion Kamvas Pro 24. Just switched off and on again as I'm writing this.

Driving me crazy! and started the moment I upgraded to 15.2 last night.

Really shocking that these kind of issues are allowed to persist.

Trillion dollar company and shoddy, untested updates. Classic.

Didn't work for me.

Just tried this with my wife's MacBook (M1, 8GB RAM, Sequoia 15.3.1 - she doesn't need an external monitor) and the same LG 29UM69G monitor:

• Connected the LG monitor for about 10 minutes, problem manifested
• Hard-deleted `/Library/Preferences/com.apple.windowserver.displays.plist`
• Shut down MacBook, waited a few seconds
• Started MacBook again, connected the LG monitor, problem manifested within 5 minutes

This problem started for me today (April 2, 2025) after updating to Sequoia 15.4 overnight. I have two identical Sceptre C27 monitors, and the one I use as "Extended Display" goes black periodically with no warning. It stays black for a short while and returns, but now I don't trust it. I'm using a HDMI cable, Mac Mini M1, 16GN memory, wall-mounted monitor.

I've never had this problem before, and only the second monitor seems to be affected. The first monitor is working normally. I tried adjusting the refresh rate (currently at 75 Hertz), but that doesn't solve the problem. I've also restarted the Mac several times with no fix. The current resolution for the working monitor is set at 1920 x 1080—going to a different resolution does NOT help. Changing the refresh rate does NOT help.

UPDATE: I swapped the cables on the monitors (Monitor 2 was plugged directly into the Mac mini, Monitor 1 into a Dock, and replicated the problem from Monitor 1 to Monitor 2. I'm starting to think the update broke my Display Port on my Mac Mini!

It's very disappointing to see this issue is not being heard by Apple and this post started in December last year (6 months already). I recently updated directly to macOS Sequoia 15.5 (24F74) and my external monitor LG Ultragear™ 32GS60QC is no longer detected by by M1 2021 Macbook Air.

Is there a way we can take this up with Apple support? I tried a few things from the earlier comments like renaming com.apple.windowserver.displays.plist file and rebooting - the display shows up with my wallpaper on it but it is still not detected in Display settings and I couldn't use it. It is seriously hampering the way I used to work and with no resolution in sight I think downgrading OS to an earlier version might just work. It will be an unnecessary hassle though. I never ever have faced this kind of situation using windows OS machines.

Hey,

Had this exact issue after updating to sequoia 15.5 on my M4 macbook; my external LG display went from always being recognized automatically through usb-c to not being recognized at all (not charging nor displaying anything). Tried deleting the .plist file and restarting my mac but that didn't work.

What did work for me was:

1. Using hdmi-hdmi rather than usbc-usbc. This worked but was obviously still super annoying since now I would need a power cord as well rather than charging from usb-c, and the hdmi cable is way bulkier. So I kept trying.
2. Unplugging power from my monitor and then plugging it back in. Still no clue how this helped my mac find it since clearly the update was what broke it, but I'll take it

A bit disappointed with the fact that an update could break things like this, had to spend more than an hour fixing it...

Dear all,

I just upgraded to Sequoia 15.5 and our old external display (a TV/Monitor) showed the same flickering error, which was mentioned by many of you. This is very disturbing and shame on Apple that they still not worked out a solution.

After many tries, a simple change solved (sort of) the issue: The old screen's default resolution was changed to 1080p and after that to 720p. These both worked, no flickering. If the resolution was changed back to the default value (1366x768 ok, i know, it is ancient...) it was flickering very badly. Strange.

Hey guys,

I started to experience the same issue when updating my MacBook Pro to Sequoia 15.6. I've since resolved this issue for myself. I don't work for Apple in any way, so please don't get super mad at me if any of these things don't end up working for you...

Unplug EVERYTHING from your device, to include the charging cable.

I deleted these files:

• • /Library/Preferences/com.apple.windowserver.*
  • /Users/<USERNAME>/Library/Preferences/ByHost/com.apple.windowserver.*
  • /Library/Preferences/com.apple.dock.*
  • /Users/<USERNAME>/Library/Preferences/ByHost/com.apple.dock.*

I think there might be a chance that other folks docks might have a different "com.apple." file associated with it. I don't know what those would be...

When restarting the device, I reset the NVRAM. I have an Intel processor, so to do that, when restarting, I have to hold down the Option + Command + P + R keys.

See this link for more info on that: Reset NVRAM on your Mac - Apple Support

I let the device completely boot up and let it sit for a few minutes. Then plugged in the dock, then plugged in the HDMI cable. Works fine now... I've read on some of these forums that the issue reoccurs over time. Fingers crossed that doesn't happens.

Hope this helps. Cheers!

I'm still having the same issue. I have a Dell P2213 monitor connected via DisplayPort and USB-C, and it stopped working after an update. I've tried deleting the Windows Server file, but it didn't work. I've unplugged the power cable and restarted, but it still didn't work. I hope someone has a solution. I`m using a Mac Mini M2.

Update: I bought a DVI to HDMI cable (my monitor is a DELL that supports DVI). I connected it to my Baseus DOCK that has an HDMI input. That's it, the monitor started working. But using the display port with USB-C still doesn't work, either on the DOCK or directly on the MAC Mini M2.