Monterey 12.0.1. Second Monitor Issue

12.1 is out and is supposed to address some issues with external monitors. Please tell us if that fixed it for you ;)

That's interesting, however the problem you are describing was exactly my issue as well - and after connecting the Apple brand adapter, the issue has resolved.

Yes, reboot and completely power off/on the system still workaround for me.

Please try to do a full shutdown of the system and then start - the second monitor should work. For me, it doesn't seem to work if I do a Restart.

Had the same issue, MacBook pro Retina 2015, Monterey 12.3. Safe boot seem to clear the issue, will continue to monitor. How to use safe mode on your Mac - Apple Support

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 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.

OK .. So, this will be a stretch. But, because it worked like magic, I'm just gonna' throw it out there for ya'.

I rarely stream. Though, I do every once in a while.

Did a second screen work on Big Sur ?

Yes.

Once I upgraded to Monterey .. It stopped like what everyone's been claiming recently. So, I do have the same problem.

My 2017 iMac does not see the monitor at all.

Period.

Not after the upgrade to Monterey.

I did try almost everything that everyone suggested. Unplugging wires .. Repluggin'em .. Restarting, then doing the same process all over again. I tried many things that did not work. Until I really got frustrated and let the whole thing go.

I lost hope. But, then came that time when I thought about streaming again.

So, I opened Twitch Studio. Which I usually use the second monitor for so I'd see what my stream looked like for viewers.

The minute I started the application the second monitor just turned on automatically. No questions asked.

It was very surprising. I went to check system preferences displays settings. It's all there and I can control everything about it like before.

As much as I'm happy that it worked again; I'm still mad at the upgrade for not letting this work as smoothly as before. I shouldn't need an application ask for a display to have it work as normal as it's supposed to without any prompt.

Anyway,

It now works even without Twitch Studio on. It simply fixed it for me. Feels like a mistake if I try to unplug anything now. Not sure when I'll push myself to do it and see if it's gonna' mess it up again or not :|

..

My suggestion for you if you don't even care about streaming is:

Just download Twitch Studio .. install it .. run it .. see if it fixes your second monitor issue. Then, delete it if you want to.

https://www.twitch.tv/broadcast/studio

Might & might not work for you. Though, you got nothing to lose if you try.

I hope this helps .. I know how frustrating it can get :|

Good Luck !!

Apple .. I still love you .. But .. you know :/

Have a good day, everyone :)

I’ve spent time with the Apple help desk. We tried a number of things. But the best was to set up a new user with administration rights. Shutdown, login as the new user, then connect the external monitors, and swap back to my user ID. All a bit shonky, but for now it seems to be working.

I also installed this app which seems to be helping:https://github.com/waydabber/BetterDummy

I had exactly the same issues as everyone else on this thread, downloaded Monterey onto a 2015 macbook, and my 2x Dell 24inch external displays did not work. I tried almost every step that is listed on this thread with and without Apple engineers' help and nothing worked. I was just about to go back to a prior OS when an engineer asked me the simplest question, whether I'd reinstalled my drivers for the displays since the software update. I hadn't. We did this and it worked straight away. When i reboot the computer the screens do not work, but if I go to the display driver manager and double click it, then they come back to life. A bit of a faf, but much better than not having my screens. Maybe I'm the only person this helps, but if it helps one other person it has been worth writing it!! Thanks to everyone for putting their ideas down as well, it has been a very helpful thread in what has been an enormously frustrating 24 hours!!

I updated to Monterey 12.2 yesterday and tried with an Apple Adapter USB-C to VGA and it works!!!! It didn't work in the previous Monterey version.

By the way, I am connecting a MacBook Pro 2019 to a external Dell 1908FP monitor.

I had this same issue upgrading from Catalina to Monterey 12.2.1 on my 2020 27" iMac and a 2nd BenQ monitor using usbc to display port cable. After following Apple's suggestions with no luck, I downloaded BenQ's DisplayPilot. Still no luck. Restarted several times and unplugged the cable several times. No luck. And then on one last unplug/plug the second monitor miraculously came to life! I don't know which of my actions fixed the problem - but it now works. I hate upgrading the MacOS - always issues but I had to to support a new thunderbolt hub. Hopefully installing the hub will go smoother.

If this is still an issue, I found a fix for mine here: https://discussions.apple.com/thread/253326025

I'm running dual displays on a Mac Mini. Just upgraded to Monterey.

Restart gives me on display #1

Full shut down and start gives me both displays

Very weird!!!