External Monitor Issue After macOS Sequoia 15.1.1 Update

I updated my M1 MacBook Pro MAX to Sequoia last week and ever since my external monitor (via usb-c) does not work properly after the machine sleeps. After the machine sleeps both the external monitor and the built in screen become very low resolution (800x600 I think) and mirrored. None of the display options or resolution settings are able to return to the proper resolutions. The only solution is to unplug the external monitor and plug it back in again. This is very annoying each time I go for a cup of tea... The workaround is to prevent the machine from sleeping, but then I have to remember to go back into the battery settings to do it at the end of a day and I usually forget...

Is there something I have missed? I have never had this issue with previous versions of macOS on this machine and monitor setup (since 2021). Surely a new OS version should be better than the last - not with bugs like this.

Just another data point.

I have an M1 mini with an LG 24MD4KLB-B connected via Thunderbolt and a Dell U3011 connected via HDMI, and a 15" M3 MacBook Air with another LG 24MD4KLB-B connected via Thunderbolt.

Both computers have worked perfectly with the external displays. The mini has gone from Big Sur to Sequoia without issues; the Air shipped with Sequoia.

I also have a 2019 Intel MacBook Pro with an external display connected via USB-C dock and HDMI, and it has been fine with both Ventura and Sequoia.

All three computers have 16GB of RAM.

Have this exact issue! 2018 Macbook Pro with touchscreen. I should have not updated at all!

At first when the screen started flickering I thought it was a hardware problem but it was out of nowhere and eventually the screen completely stopped working. It only works at a certain angle so I have to stick to using an external monitor but now with the latest updates even that doesn't work. My macbook won't recognize my external monitor no matter what I do. How are we supposed to work with these huge and important issues with our Macs? If Apple won't even officially refer to this issue, I will believe this is purposefully not being fixed to force users to buy new PCs! I will never buy an Apple product again ever if they don't fix this asap!

Similar problem here, my external display works fine when my MacBook Pro boots but after the computer goes to sleep/lock mode the external display stops working. By restarting the computer the problem is solved temporary but it happens every time.

Same here with Mac mini (intel & M1) with displays connected via USB-C and Sequoia 15.3.2. We're using them for digital signage and it's really a mess! I'm afraid buying the new Mac Studio and connecting 6 display will not work...

Is there any solution right now?

I just found this thread after experiencing issues with my Eizo monitor and a MacBook M3 Pro after upgrading to Sequoia 15.4. I am now at 15.4.1 and the issue persists. The external monitor screen goes black when it used to be grey. I can still use Photoshop on top of this black background, however I don't like it and it isn't helpful for colour correction which is essential to my work. If I restart my computer, the monitor screen will become grey again, though this is temporary. Furthermore, Color Navigator, the colour management software for the monitor is not making the connection anymore which is crucial to me. Are there any new fixes to try? Thx.

Well done Apple, with the last update Sequoia 15.4.1 now it works even worst than before.

Now it stops working each time the macbook goes to sleep mode.

Please fix this soon is impossible to work like this.

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.

This is still not fixed! I updated from 14.x to 15.5. Right after updating my external 4k monitor started going black every now an then. W T F? Apple support line played dumb, iE "not a know issue". I considering going back to linux.

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.

Update: There are times when the monitor with the DVI to HDMI cable connected to the Baseus DOCK starts to look all gray and dusty. Then I turn it off and on, and it starts working again. But honestly, I'm worried.

After updating to Sequoia 15.6.1 (24G90) my Kamvas Pro 16 (2.5) stopped working as a display - it's still working as a tablet, but no display is showing up in the macOS display settings. I've tried all the fixes, but it's still broken. I checked if it's still working on my macbook air with Sonoma - it works fine. It's 100% an Sequoia Issue.

How do that on Mac Air M2? I've only had the mac since march. Still learning and system search didn't bring anything up?

I experienced the same initially when switching to HDMI using a cheap multi-functional adapter. For an entire day, no flicker! Then the next day, it started all over...