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

So this is related to a previous long-standing bug with DisplayPort, which forced all of us to go into our monitor settings and switch from DP1.4 to DP1.2 so our external monitors would work. Apparently in "fixing" this bug, Apple decided that checking autonegotiation was redundant and the user needs to manually fix things.

The solution is to set your monitor to DP1.4. For a BenQ monitor, that is going to suck, because if you don't have a valid source input, it won't give you the display settings menu. You'll need to hook up a second computer to the monitor without macOS 12.3 so the monitor has a signal, then go into the menus (System -> Advanced -> DisplayPort) and switch back to DP 1.4. Your monitors will work.

I'm so happy to have had to troubleshoot this in the middle of a workday. It was problems like this that caused me to switch from Windows to Mac over twenty years ago.

Updated my iMac last night. Same issue. I have two LG monitors connected via DP through a CalDigital dock. The CalDigit connects to the iMac via a usb-c connection. After the update ALL monitors including the laptop were black and would display nothing.

I had to, as suggested by others, use the Settings menu on the monitor itself to swap to Display Port Protocol version 1.2. Then disconnect and reconnect the usb-c cable from the Mac. After a reset, and reconnect monitors work again. They were both previously configured for Display Port Protocol v1.4. So - something in the 12.3 update is messing up that protocol negotiation.

Another user in another forum pointed this out to me and it... worked?

Disconnect your monitor

Unplug your monitor

Wait a minute or two

Plug your monitor back in

Connect your monitor

This... seems to have worked for me after trying all the more complex solutions (safe mode etc.)

Now solved with Apple Support.

Update 12.3.1 did not solve it for me.

No black screen, but frozen screen.

We had to remove 2 specific prefs files, reboot the computer and now ok.

Taken steps:

In your SSD or HD:  system library - preferences - look for com.apple.windowserver.plist - remove it

Also on your user library -  via hidden key press: go to the Finder - click  in top menu on Go - press key option on the keyboard - choose Library - Preferences - ByHost - com.apple.windowserver.plist - remove it

Advice: contact Apple Support if you are not easy with this to execute on your own.

Reboot - it should now be ok

In my case this solved it.

I assume there will be another minor Monterey update because of this

@emmanuel-0_0, the most current version is 12.4 and includes fixes for the monitor issue. I had to reset my second display to factory settings and after that it has worked normally. Because it was not working I could not access the menu until I connected it to an older MacBook on Catalina I have laying around. Once connected, I reset to factory and works great now. If you can reset your monitor and update to 12.4 you might have better luck.

Spoke with Senior level technician Chuck, about this. Two different senior technicians said this is a known problem and the engineers are investigating. Here is how we got my monitor working again.

1) Under energy savings we slide the rule to "Never" and ensured the screen saver was working.

2) Ensured the screen saver was active

3) Checked "System Preferences/Displays" and noticed that only one display was connected to the Thuderbolt Display Port (HUB).

4) Confirmed that only one display was connected by viewing the System Report under "About this Mac"

5) Shut down the MacMini

6) Held the shift key down while starting the Macmini to get into safe mode.

7) Checked System Report and Display preferences and now I see two monitors again

According to Chuck they are looking for a bug around the energy savings features and this is a work-a-round

Apple - you have purposefully made this as hard f*****g possible to remediate because, unlike Windows, you are so arrogant in your OS updates (that you clearly do not QA at all), that you offer no downgrade option. ALL - this is the definitive solution that I employed THREE (3) WEEKS prior and I have not had ANY issues since then,

1. Backup your entire SSD via direct connected Time Machine. If you are like me with a large SSD, congrats, APPLE FORCED YOU TOO, to spend $500+ on on an Samsung 4TB external SSD (link) where you can use this USB-C to SATA connector (link) - all regular links to US Amazon; sadly, I have no referral code/links.
2. Download version 12.1 from this site (link)
3. Create a bootable install USB key (link)
4. Boot into safe or recovery mode and re-partition your entire SSD (this wipes the entire computer FYI, but is the ONLY OPTION APPLE has made available at all...)
   1. FYI - at this point I recommend that you just hardware your laptop into your router or switch and bypass Wi-Fi; its faster and easier.
5. Set up the "new laptop" as fast a possible; your going to wipe the entire "new"/"temp" user anyway.
6. Restore Mac from Time Machine backup (link) - delete that temporary user from the prior step; wait like 4 hours maybe (that's about how long my 3.4TB SSD restore took.
7. No more issues. For weeks, blissfully easy use once again.

** Apple, you owe me 20+ lost billable hours or work, at least many hours in lost work, and over $500 for having to purchase equipment only need to remedy your insane f*** u*; congratulations, QA and OS teams - those I doubt you were the ones who made the decision to focus on continually increasing levels of completely dumbs**t; but at least we have a **** ANIMOJI...might as well be your new logo.

Same issue. HP32 4K.

Not a single solution worked - neither dropping to DP1.2, nor reconnecting monitor, nor resetting NVM and this kind of stuff.

Only working solution for now is connecting monitor via dockstation hdmi port. This is the only thing waking monitor up.

Neither usb-c to usb-c nor DP to usb-c cables are working anymore.

Using Mac 10+ years first time i come across something so basic being broken ... Total disaster that affects everyone and MUST BE fixed 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).

Same with Mac Mini Intel and monitor LG 34WK95U  UltraWide 5K.

No problem with monitor Iiyama PL2773HD 27inch.

When I boot in safe mode there is no problem with the LG monitor.

When I add another standard user account: no problem with the LG monitor.

So it seems my standard user account which i used during the Monterey update is somehow damaged because of that Monterey update.

Tried to remove the caches etc. to see if it would help but no luck.

So I have some workarounds but not that nice.

I had contacted Apple Support.

We assumed there is something damaged in the used account during the upgrade proces but no fix yet available.

I amusing MacBook Pro 2018 intel with an HP U32 4k external display. It was running just fine for almost a month since I got the external display. I was using thunderbolt port and USB-C 3.2 cable. The display stopped working right after the update to Monterey 12.3. I spent few hours with the Apple tech support and they failed to fix the issue after reinstalling the OS. Apple tech support referred me to contact HP for driver update which was clearly not the case of the external display failure.

I then rolled back to the previous version of the MacOS. Luckily the MacBook was able to detect the external display and working just fine like before.

I hope Apple will be able to release an update for this issue.

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

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.

The problem with a factory reset is that you need an image to actually get into the menu (at least on my monitor).

I've tried everything: Unplug while running, unplug while not running, leave it unplugged for a while, plug in while running, turn on before switching on the Mac Mini, turn on once there's an image on the main monitor,... - nothing helped, apart from using the official adapter. And please, don't spend money on that adapter, call support, so they can send it to you to test (if you haven't yet, of course) - maybe that'll make them more interested in this problem.

I had the same problem. After updating to 12.3.1, my external monitor that I have been using since 2018 no longer worked. I found an article(https://www.howtoisolve.com/fix-mac-second-monitor-issue/) that helped. After turning off Automatic Graphics Switching, rebooting, and then plugging my monitor back in, my monitor was detected.