Monterey 12.3.1 External Monitor/Display Issue - No Longer Outputting Signal

Took me a whole day to get to the bottom of this and fix it up:

1. Unplug every connectors
2. Restore Factory Setting of the Monitor (if its a smart monitor, else ignore)
3. Enter Macbook Safe mode
4. Delete the files with ".windowserver" from Macbook (for example: com.apple.windowserver.plistxxxxx)
5. Reboot Macbook into normal mode
6. Connect the monitor to the screen
7. Bazinga! it works now

Monitor: Dell U4021QW

Both on macOS 12.3.1:

• 15" MacBook Pro 2017 Intel via USB-C: PD, no USB, no video
• 14" MacBook Pro 2021 ARM via USB-C: PD, no USB, no video

This issue is likely specific to DisplayPort Alt Mode (DP via USB-C) as USB-C to HDMI adapters/cables work (HDMI Alt Mode). It might be specific to DP 1.4 mode, as some users report that setting their monitor to use DP 1.2 does work. Not all monitors have that option, including mine so I can't use that as a workaround. 

Everyone, please do create your own case with Apple Support to get more attention to this issue!

@OP: please update the title to reflect 12.3.1

Keep:

• Contacting Apple Support and open tickets
• Indicate "I have this question too" on the top post of this thread

Try:

• Reboot
• Unplug power cord from monitor (not just a power button/switch)
• Different USB-C cable
• All different USB-C ports

You could also try the public beta of macOS 12.4 and see if that makes a difference.

I want to re-post a workaround using hdmi and airplay I found in case it is helpful until Apple decides this is important enough to fix.

If you have an Apple TV:

• with hdmi connected to your computer and not working monitor, go to displays in system preferences
• choose "add display" lower left and "mirror or extend to" your apple tv
• unplug hdmi out from computer and plug into Apple TV in
• wait for signal on your display
• once you have signal, unplug and re-attach hdmi to your computer
• wait for display to show (now airplay) signal
• in displays system preferences again choose "Display Settings..."
• disconnect airplay, wait for original, pre 12.3.1 signal (mine takes about 5 seconds to 'register')
• done

This works for me. It's a pain but it works. I have to change my power settings to not allow display to go to sleep or else I have to do it all over again.

Hope that is helpful, and hope Apple starts to think user experience is valuable to them as a company again.

Give this a try:

preconditions: MAC is off. Monitor is off and power is unplugged.

• Connect the monitor into the MAC via Thunderbolt cable
• Plug in the monitor into power
• Switch on the monitor on with the usual power button on the monitor
• Switch on the MAC (press the power button)
• login to the MAC
• Unplug the monitor from power (without switching it off), meaning just unplug the power cable.
• Wait a few seconds
• Plug in the monitor back into power. Remember the monitor is still switched on. So you should see now the usual small power-on light on the monitor
• Check the MAC now if its connected to the monitor now.

Perhaps for those who might not have found newer drivers

or other links online, with workable solutions for your kit; a

repeat from a few users contributions here. And links from

more recent updates, could help some. (DisplayLink driver

access is related to OWC product, in this presentation.)

There is a partial hardware fix. Plus: links within, to driver

& software (display link, from recent month) to consider.

And the OWC mac-centric supplier of renown again shows

a path could exist with their 'Display' link adapter and driver.

OWC USB-C Dual HDMI 4K Display Adapter ~ with DisplayLink

for Apple silicon M1 & M2 Macs or other Macs or PCs with USB-C or Thunderbolt

https://eshop.macsales.com/item/OWC/CADPDL2HDMI/ [$119.]

(This brand claims to 'guarantee it will work' & offers support

to those looking for solutions; without buying anything first.)

..If you already bought an adapter from OWC, notice new software..

Drivers and downloads from Synaptics: for macOS and Other OS:

DisplayLink Downloads Page | Synaptics

https://www.synaptics.com/products/displaylink-graphics/downloads

[This, made available from link within the OWC product portal.]

All macOS product downloads

DisplayLink macOS Software

https://www.synaptics.com/displaylink/downloads/macos

macOS DisplayLink Manager (newer DL drivers & download)

"DisplayLink Manager Graphics Connectivity"

for: Ventura 13, Monterey 12, Big Sur 11

Release: 1.8 | Oct 24, 2022 [see all "Legacy Releases +" via toggle]

DisplayLink macOS Software for Downloads Section | Synaptics

https://www.synaptics.com/products/displaylink-graphics/downloads/macos

"DisplayLink Manager is a new way to enable your DisplayLink dock, adapter

or monitor on macOS platforms. It's an application that combines our latest

driver with features that streamline the setup of mutliple displays up to 4K."

[Synaptic sites default files release notes Txt 2022-10/DisplayLink manager graphics connectivity1.8]

Hopeful this may help some, who keep trying whatever they found. Either

had one, that only worked in one specific time; or didn't get that fix at all.

.& hope this 'quiets' some emails from non-unsubscribable ASC threads.

Similar problem with Mac mini (2018) + LG 34BL850 with USB-C.

After the upgrade, things work from the moment Mac mini boots until the first standby. When mac switches to standby and awakes from it, the display doesn't get a signal, hard restart is needed.

After the hard restart, there is a diagnostic window about segmentation fault: "window server Termination Reason: Namespace SIGNAL, Code 11 Segmentation fault: 11".

Same problem after upgrading to 12.3. Was using a portable external display driven through the thunderbolt usb-c cable. Not keep on saying no signal!!! I really regret upgrading and this is how you break customer's confidence in your product.

Same Issue here as well!

Mac Mini 2018 with BenQ PD3220U. Thunderbolt 3 used at both ends. Tried also HDMI.

Tried all solutions I have found here and at other sites.

Fortunately I did run a SuperDuper backup before upgrading to OS 12.3 so therefore I am now back at 12.2.1 again.

Does anyone at Apple read these cries out for help or do we have to mail bomb Apple Support?

Same issue here! I've got a Mac Mini 2020 with the same setup I used on my old Mac Mini: Main monitor connected via HDMI, second monitor connected via DVI->USB-C adapter. It worked there but doesn't work on this one. I already updated from 12.0.1 to 12.3 and now it displays the correct monitor information for the second monitor (previously it said that the second monitor is a 46" one?!) but when I switch it on, I still only get the "No Signal" message and then the monitor switches to sleep mode (I can still move the mouse cursor to it).

Same issue here.

Macmini i5 2018 + LG 4K display

After updating my display went black after logging. It back to work when I plugged it on HDMI port WHILE USB C is connected.

After I connected the display on two ports and I got it alive, I changed its resolution to standard res (4K zoomed to looks like 1080p) or pure 4K and it works!

On any scaled res it goes black.

But my fix is not fully functional. When my computer goes to sleep, my display doesn’t wake up.

Please guys, open the Feedback Assistant and report the bug to Apple

I have the same issue with my iMac when I upgraded it to macOS 12.3 from that time my external USB-C monitor is not detected and displayed a "No Signal" error. while it works with some of the USB-C to HDMI adaptors.

The same monitor and the same USB-C cable is working properly on my MacBook that its macOS is not upgraded.

Another interesting thing is that even some of the USB-C to HDMI adapters are not also working with my upgraded computer while those are working with my MacBook with a downer macOS version!

I already check all the things on the apple checklist and had talked 3 times with the apple support.

If somebody has a solution please let me know.

Same issue here with a MacBook Pro 13-inch and an external monitor from LG which is connected with DisplayPort. Since the update to 12.3 there was no signal.

I tried different solutions but they laat one was working for me to move from DisplayPort to HDMI

Monitor: 49" CRG9 Dual QHD Curved QLED Gaming Monitor

Equally experiencing this frustrating issue after updating to 12.3 on MacBook Pro (16-inch, 2019). HDMI works via the dock station, but the resolution and color is so bad that my eyes hurts! Apple needs to resolve this ASAP.

Finally got it fixed. Unplugging the monitor for over 5 minutes didn't help. I connected my monitor to another Mac (12.1). Changed the DP version from 1.1 to 1.4. Then it started working on the updated Mac (12.3).