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

I had this same problem and could not find answers online. I am running Monterey 12.3.1 on a MacBook Pro16 with an LG 34WN80C monitor connected to the Mac with USB-C cable. I went to the monitor controls and after I verified that is was set to use the USB-C port, it suddenly connected. The Mac was connected by cable when I did this. No changes were made in any settings, I was just verifying the monitor setting. Really weird and doesn't make sense, but I'm now able to use the monitor.

I hope this helps someone else out there!

Was having same issue. Macbook pro 12.3.1 with LG monitor.

Thanks to everyone for suggestions - which i tried.

I tried the unplugging it and cable as suggested - didn't make difference.

I tried the Reset on the monitor - didn't make difference

But then i just unplugged the cable from macbook to monitor again and it worked. So i would suggest trying what i did and if you don't see it right away, try the cables again etc. Might work.

@emmanuel-0_0 how do you connect your mac to your display? Mac-thunderbolt (usb-c) to Monitor-usb-c? If so, try to connect your Mac-thunderbolt(usb-c) to Monitor-HDMI. You have to get a usb-c to HDMI-cable or a usb-c-To-Hdmi-Adapter. I've read comments here that this worked for some folks. Give it a try.

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.

I fixed the problem for time being with downgrading the DisplayPort version from 1.4 to 1.2

Not a 100% but this approach works best for me.

• plug power into macbook and wake up
• turn on monitor (odyssey g9)
• when monitor osd is visible, plug in usb-c dock/cable

Try 12.4 its out

After upgrading to Monterey 12.4 the problem was resolved, for the first week -- now I am still occasionally getting the monitor dropping but much less frequently than with 12.3.

Exact same issue and the only "solution" is to reboot into safe mode and then again into normal mode

The whole thing seems to be random. I contacted Apple support (do that too, everyone!) and shared my screen with them and they actually saw the second screen, while I didn't. When I then set the second monitor to mirror my main one, the image was there all of a sudden (tried that before, didn't work). After a restart the image on the second monitor was gone again and mirror mode didn't bring it back. The support guy had me try a couple of things (safe modus, create a second admin user, unplug the cable,...) but nothing worked. The Mac went to sleep and when I just woke it back up, the image was back again all of a sudden (even on the login screen) - I bet a restart'll bring back the "No Signal" message though (edit: yes, "No Signal" again).

This thread was helpful. Changing from DP 1.4 to DP 1.2 worked. But before this upgrade the second monitor would go to sleep and not wake up, so I have been setting the computer to let the monitors go to sleep. I do not know if the fix resolved the sleep issue.

Mac mini (2018)

3.2 GHz 6-Core Intel Core i7

64 GB 2667 MHz DDR4

LG UltraFine (27")

LG HDR 4K (32")

I could get my external display working only after I have enabled sidecar to my iPad (using Add Display option in Display settings). But sad thing is that external display gets disconnected as soon as I disconnect iPad as display.

I didn't expect Apple to build such a messy update. Shame on Apple...

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

I finally received the multiport adapter I'd been promised (this one) and guess what: My second monitor is consistently receiving a signal again - it doesn't matter if I use the HDMI cable directly or a DVI-HDMI cable with the adapter, it's working, even after multiple restarts! You can't use the adapter's USB-C port to connect the second monitor too though but only the HDMI port. Looks like Apple added something to MacOS 12 to keep people from using third party adapters to get them to buy the over-priced $70 one (or maybe they messed it up on accident and now simply don't want to fix it, who knows)! Everyone who's still got the problem: Ask your rep to send you that adapter too, so you can test it!

That's weird, it worked instantly for me and the image was still there after multiple restarts. Did you get the same adapter I linked? Did you try other USB-C ports too? Did you also try a different HDMI cable, maybe yours is causing additional problems with the new MacBook?

Btw, I tested my regular non-Apple adapter with my old Mac Mini (that's still got Big Sur) again yesterday and it was still working fine with my regular two-monitor setup, so it's definitely Monterey and/or something in the new Mac Mini causing the problem.