Monterey 12.0.1. Second Monitor Issue

call apple and ask for a senior tech. Talked me through a series of solutions. All is well. Took maybe 15 minutes tops

Mine self-corrected. Though I did do some restarts and the Sys Pref thing about Battery check and uncheck. Go figure! It's working normally now.

My m1 MacBook Air can't see any external monitor when plugged in via USB-C. Weirdly, it could see it when a hub was attached and HDMI was used.

I've decided to downgrade to Big Sur until this fixed. Big Sur will always recognize an external monitor.

scrawley1, Apple has had several people call me about this. I deleted all third-party launch agents/daemons from multiple locations, but it didn't help me and my 2019 MacBook Pro 16" with macOS 12.0.1 (and now 12.1). This monitor problem is quite intermittent, so I'm guessing it'll come back to haunt you again. It occurs less frequently if I connect my external screen directly to my Mac with a USB-C cable, bypassing my Caldigit TS3 Plus hub, but it definitely still happens...and infuriates me each and every time.

Did Apple ask you to type the `sudo sysdiagnose` command and upload the 300MB report to them? I did that a couple times. A man named Pedro didn't even thank me for the hours I spent acting as Apple's unpaid QA minion. ☹️

I just upgraded to 12.1 yesterday and immediately encountered this issue. I have a 34" Asus USB-C 21:9 ultra widescreen that has worked perfectly up till I updated the OS. Now if I go fullscreen on any app with that monitor the screen flickers on and off, it's completely unusable. Luckily if I don't fullscreen the app, but this needs to be fixed. I'm glad to see I'm not the only one encountering this.

Prior to this update the monitor worked fine. I work remotely for work using Microsoft RDP and it was great, RDP used all available screens at native resolution. I cannot utilize that feature any longer, I must either adapt to this bug or downgrade. I thought it was just Microsoft RDP that was causing it since if I left fullscreen it stopped. But then I went fullscreen on a youtube video with google chrome and the flickering returned. So this is definitely an Apple issue introduced in the OS 12 update.

Please fix this Apple. There are 8 pages of this issue since November.

Apple's senior tech advisor called me yesterday. He said the next thing to try is to do a clean install of Monterey 12.1. I backed up all my files to TimeMachine and did the clean install. Advice was not to restore files from TimeMachine backup during the install. I made a new user during the install and not to use Apple ID as was told and guess what... the same problem still exists.

All my drives connected to Dell Ultrasharp's USB hub were connected using the USB-C cable but no signal on the display. Apple promised to send a free USB-C Digital AV Multiport adapter that 'usually solves the problem' as he said. I'm now waiting for the adapter and keep you guys updated if that helps. I am still waiting for the real solution to this annoying problem.

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

Oh boy, so after a few hours of trying all the tricks here and in other places on the good ole' internet I was about to give up. Same issue as many of you, second monitor running through a Dell Hub, is that what it's called? Like a docking station but nothing docks in it. Anyway...y'all get me I am sure, nerds. Monitor won't stop flickering black along with my Macbook Pro, totally unusable. So I'm ready to give up but then the genius in me pops up and says "hey d-head, try popping the lightning/thunderbolt/usb-C thing through an adapter to regular USB then back to lightning/thunderbolt/usb-C thing. Yup. That worked. My 2nd monitor now looks like a hillbilly set it up but at least it is working through the Dell hub whatchamacallit thing. Steve Jobs is literally going to come back as a zombie and take a flame thrower to all the people ruining Apple. Horrible, just horrible. Although, this is sort of on me for upgrading. Every-time I upgrade Apple SW I trade one problem for 10, SMH, anyway, hope this helps somebody. peace out.

Sorry, another one:

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)..

I wish these tips worked, but they don't. Since updating to MacOS 12.0.1 Monterey, my MacBook Pro can rarely connect to my Dell U-Series 38" Screen LED-Lit Monitor (U3818DW) external display. On boot up, the laptop LED screen briefly flashes about every 4 seconds as the laptop tries to display a background and dock on the Dell external monitor. Very rarely, after more than 10 tries, the laptop can connect. I can only use the monitor by going into clamshell mode. Sometimes I can start in clamshell mode, then open the laptop lid, making both displays work. Laptop is a MacBook Pro (16-inch, 2019) with 2.4 GHz 8-Core Intel Core i9, 64 GB 2667 MHz DDR4, AMD Radeon Pro 5500M 8 GB. Never had any trouble with previous OS. I see that there were many reports of this problem in Beta. Good stream on Reddit reports that fixes were attempted.

I have this issue as well. I connected the second display to another MacBook Pro with Catalina installed, and had no issue with the display working.

Only happened when I updated this morning to Monterey.

I have the same issue just to pile on. I've tried all the fixes above. I can get an external monitor working only by plugging in directly, and I have to bring up the second external monitor wirelessly. I don't know how much noise needs to be made before Apple figures out a fix on this.

This feels like old apple right now, where you couldn't trust the updates. I don't want to have to go back to manually updating all my devices after the second or third iteration comes out and all these bugs are fixed.

This is really poor on apple's part that there's not a bug fix for this yet. I've been checking to see if the software update is available for almost a month now.

I wanted to give everyone an update on this unresolved issue. I received several missed calls and email correspondence from Apple Support and finally arranged a phone call yesterday (12/2). The point of the call was to gather details about my issue (our issue) with Monterey not allowing our Macs to recognize a second monitor. Alex from Apple Support reached out to me as a direct result of this thread. So, Apple is aware and a patch is in the works. I hope this news gives you some solace.

I'm in the same boat. After contacting Apple they sent me one of their USB-C to HDMI adaptors and that fixed the problem for a while. Now, my external monitor picture flashes on and off every few seconds.