Monterey 12.0.1. Second Monitor Issue

I have the same problem here On a Mac mini M1.

It was working fine with Big Sur and started to fail after being upgraded to Monterey.

After several hours of tests (first thinking that I forgot something myself), I'm fed up and I give up.

Note that I Also have a Mac Air M1. When I try to copy screens to it from the Mini, The second Screen of the mini start to work, displaying a copy of one the other screens (1st screen of Mini or screen of Air, depending of the display parameter I try).

So there is something looking like a dysfunction with the share screen capability.

The only solution from now seems to be to downgrade to Big Sur. It's such a shame ! Just when I started to thing that MacOs was not so bad.

When I read that the only proposition is "Disconnect the cable from your external display from your Mac, then reconnect it. If the cable from your external display doesn't connect to the ports on your Mac, you can use a Thunderbolt 3 or USB-C adapter.", I'm half afraid, half furious, and finally very sad.

I have this same issue immediately after upgrading and have tried everything, including all the tips mentioned above. I am on multiple deadlines for graphic design projects and cannot utilize my second monitor. BOTH of my screens fade to black and my MacBookPro screen comes back on, but when the second monitor adapter is plugged into the USB C it flickers back off repeatedly. Designing on a single laptop screen is proving to be highly inconvenient. Needs a bug fix, stat.

Hi achap78,

Thank you for contacting Apple Support Communities. Based on what you stated, it seems like the second display is not working when connected to the iMac.

"Disconnect the cable from your external display from your Mac, then reconnect it. If the cable from your external display doesn't connect to the ports on your Mac, you can use a Thunderbolt 3 or USB-C adapter."

If your external display isn't detected or appears blurry on your Mac

"Connect your display to power, then connect your display to your Mac. Check the ports on your Mac to find out whether you need an adapter.

If you use an external keyboard and mouse with your Mac notebook, you can close the built-in display after you connect your external display. You might have to press a key or click your mouse to wake the external display.

If your external display doesn't turn on after you connect it to your Mac, connect your display while your Mac is off, then wake or turn on your Mac."

Connect a display to your Mac

Please don't hesitate to let us know if you need additional assistance.

Cheers.

I got it to work!

I tried in Safe Mode and my external monitor worked fine. Restarted in normal mode - still same issue and I noticed my machine wouldn't SLEEP.

I found this article (https://michaelkummer.com/tech/mac-sleep-fix/) which suggested to reset the NVRAM and System Management Controller (SMC) by shutting down the Mac and turning it back on while holding the opt + command + R + P keys.

I did this with all external USB-C (except power) disconnected, logged in and plugged in my monitor.

Don't know how long it will last, but it's working now.

kkornell wrote:

Is this response really from Apple? This is the best you got? This response is not only useless it is written as if we are third graders...Replug your device?? Really? Just admit your update is bad and promise us a date when you are going to promptly fix your mistake which is creating a big problem for your best apple market , people in the creative field that need two + displays!

This is a user-to-user technical support forum, with unpaid volunteers contributing answers. You are not talking to Apple in these forums.

If you wish to talk with Apple, then you can use: Get Support

Or Feedback

https://www.apple.com/feedback/macos.html

hi @cazal1128 ,

I'm not saying you need to get those ones in particular but I am saying that's what worked for me. I'm actually using 3 monitors and all 3 are hooked up to some USB-C dongle that allows for a display output. The one I never had trouble with is the Apple one but I bought two of the other ones I mentioned previously, now all three monitors work. I don't have any thunderbolt adapters so I can't speak to those. The apple one I have is this :

Satechi Aluminum USB-C Multiport Pro Adapter - Apple

You may even be able to find some other sort of usbc dongle that isn't as expensive as the amazon ones I posted, I just went with that one since it had pretty good reviews but once again, this is just my experience. Also, I learned that if you get a dongle that has 2 outputs (1 usbc to 2 or more video output) do not get it, those only mirror the displays.

Best of luck!

I "fixed" the issue this way:

1. Login with no attached monitor, only MB.
2. Use the PC for a few minutes, then connect the adapter first, with no monitor attached to it
3. Then after a few seconds, connect the monitor to the adapter.

It usually works, sometimes doesn't and sometime with low res, then I have to repeat the steps. But it's really annoying to do it everytime

I wish I had the link to the fix I found that worked for me so they could get the credit, but this is all I have. Not sure it will work for everyone, but worked for me.

1. Turn off the second display
2. Unplug it from Mac (I have the new Mac M1 if that makes any difference)
3. Leave it a few seconds and replug it into the back of the Mac
4. Turn the monitor back on.

Hope this helps.

I found the solution:

1. Plugged in the dongle with the HDMI connection to the LED screen (2nd monitor)
2. Turned on monitor
3. Went to System Preferences
4. Picked 'Displays' (different screen from hitting displays when monitor is not connected)
5. Hit 'Display Settings'
6. Changed the resolution to 720p
7. Changed the refresh rate to 60hz

I was able to get this to work on my mac mini by doing the following:

• Power down CPU
• Unplug thunderbolt monitor from Mac Mini
• Power up CPU
• Once you have an image and are logged on - connect the Thunderbolt monitor

I have powered down unsuccessfully, I lose the settings. But, as long as I keep the machine on - it works.

I hope this helps, this bug drove me mad for a few hours.

updated for clarity:

I was able to get this to work on my mac mini by doing the following:

• Power down CPU
• Unplug thunderbolt monitor from Mac Mini
• Make sure HDMI is plugged in to mac mini & monitor
• Power up CPU
• Once you have an image and are logged on - connect the Thunderbolt monitor

Good luck!

For anyone who facing the issue external display not working as usual via usb-c after upgrade to Monterey, for my case...

• M1 max 16" macOS version 12.1
• Dell Display U3219Q

I've found WORKaround on Reddit : https://www.reddit.com/r/macsysadmin/comments/qgypzy/comment/hpjdnn9/?utm_source=share&utm_medium=web2x&context=3

This issue still exists for me in 12.3 on an Intel (2018 T2) Mac Mini, verified as a Monterey regression. External monitors are kind of important on a Mac mini!

I always hang back on big upgrades for a few point releases as my environment is fairly complicated an early point release just burn time up doing Apple's testing for them. Issues seems to be quieting down so put my big boy pants on an upgraded to 12.3 from 11.6.5.

On 12.3 I can only have one monitor working in any boot cycle, first one wins and they just sit there flickering and failing to sync the second one every few seconds until I pull the power cord on the one that is failing to come up. Both identical Iiyama Pro-Lite XUB3493WQSU, both USB-c/Thunderbolt-3 connected (on different TB lanes on the Mac, and only 3440x1440x60/75Hz each monitor), no issues at all with anything from Mojave on until Monterey came along so definitely a software issue in this release.

Especially galling as the downgrade process is *so* broken in T2 Intel Macs. They won't downgrade restore the OS from TM backups, nothing worked for me until disowned it in Monterey and then nuked it back to its delivery era Mojave, but it still wouldn't forward upgrade from there other than to Catalina or (surprise surprise Monterey), seemed to have a total aversion to re-installing Big Sur. Completed in the end by making a USB bootable and lots of dead chicken waving. A day of my life lost and I'm still waiting for a migrate from my TM backups.

Anyway, things that didn't work that I've seen various people suggest:

• Moving one of the monitors to HDMI (made no difference).
• Power cycling in all sorts of orders.
• SMC and PRAM resets.
• Changing DP version level on monitors.
• Changing sync rates.

It is 100% repeatable, going back to any version other than Monterey resolves it. As a consequence I now have an extra Monterey volume that I can boot across to in order to reproduce the issue and would be more than happy to flush a few more hours working with someone from Apple to boot across and grab traces if it helps get some resolution, but I guess I'm going to be sticking on Big Sur for a while.

Monteray 12.3 upgrade did NOT resolve the issue. I did not mention in my previous reply, but the odd thing is that the MacBook seems to detect the External Display, but the External Display does not see a signal from the MacBook (monitor tells mom it is going into Power Save mode due to no signal on mDP). Under 12.3, same thing. See screenshots...