External display no longer recognized on MacOS 12.3

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Level 1

11 points

External display no longer recognized on MacOS 12.3

2018 Mac Book Pro 15" and I have 2 external monitors (same viewsonic model), have been using fine for just under 2 years. After updating to 12.3, one is recognized and one is not and I have no clue why. I have swapped cables, connected other devices, including a iPad Pro (all fine) I have tried all 4 ports on the machine no difference. The Mac book flashes when the unrecognized monitor is plugged in, but never displays an image. the monitor seems to think it's connected (I don't get the no signal warning) nothing.... 8* the monitor is powered and the screen it bright (bleed from the backlight). The other monitor (same exact model) connects and works fine.

Do Macs just no longer like right side monitors?

What the heck did 12.3 do to my machine?

Posted on Mar 15, 2022 10:01 AM

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Answer 1

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cowomo404 Author

Level 1

11 points

Mar 24, 2022 6:34 AM in response to cowomo404

Tried many of the suggestions below but none worked - I did solve my problem though. This is what I found - which may or may not be the same issue others are having.

My monitors are a 4k HDR panel - but I have previously turned off HDR on one of the panels (reasons not important).

My panel also doesn't allow access to the OSR without a video signal ... which made it a bit tricky to change the settings when it's not recognized; but using another machine I turned on HDR on the panel and the Mac instantly recognized. I didn't test this by turning it off again and instead just thanked my lucky stars - but it may be that the new OS requires HDR panels to send HDR signal ... or something like that. Sorry for other folks having trouble - my fix might be an area to explore.

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Answer 2

Mar 16, 2022 8:53 AM in response to cowomo404

Hello cowomo404,

It sounds like you're having trouble with you external display being recognized. First, check for any firmware updates for your displays.

Next, start up in safe mode to see if the display is detected while in safe mode: How to use safe mode on your Mac

Take care.

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Answer 3

Mar 18, 2022 7:48 AM in response to cowomo404

I did have a similar issue. External 4k Monitor connected via USB-C was not recognised after update to 12.3.

The following did help in my case.

Unplugged Monitor from Mac
Unplugged Monitor from Power
Restart of Mac
Re-plug Monitor using USB-C cable to Mac
Power-on Monitor

Since then Monitor is recognised again by the MBP M1Pro.

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Answer 4

Wbs22

Level 1

23 points

Mar 18, 2022 7:25 AM in response to cowomo404

This is how I resolved.

Here is the latest with a work-around. Reinstalling the OS did not resolve, so went old school and used an HDMI Cable to Mac Mini versus a DP or USB C and the OS booted like normal. Also display scaling is working as expected using HDMI.

Hope this helps. Likely a fix coming soon from apple, so that we can all use our USBC or DisplayPort interfaces again.

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Answer 5

Wbs22

Level 1

23 points

Mar 18, 2022 7:27 AM in response to swiss_user

This is how I resolved.

Here is the latest with a work-around. Reinstalling the OS did not resolve, so went old school and used an HDMI Cable to Mac Mini versus a DP or USB C and the OS booted like normal. Also display scaling is working as expected using HDMI.

Hope this helps. Likely a fix coming soon from apple, so that we can all use our USBC or DisplayPort interfaces again.

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Answer 6

Wbs22

Level 1

23 points

Mar 18, 2022 7:52 AM in response to Swiss_Mac

Good to hear. The issue that others have run into where unplugging/reboot does not resolve appear to be Intel Based Macs, where users have gone to the extreme of reinstalling the OS from recovery.

Support has the use case I provided submitted to their engineering/2nd level support teams to try and replicate.

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Answer 7

Mar 28, 2022 8:44 AM in response to cowomo404

I really wish I would have seen this before I updated. I have a brand new Mac Mini with two external monitors via Thunderport. Everything worked until I updated last night, now only one monitor at a time works, regardless of the port I'm using. I've tried HDMI, Thunderport and DisplayPort. So far, none of the fixes have worked.

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Answer 8

techgoat

Level 1

17 points

Mar 29, 2022 2:43 PM in response to cowomo404

I also had a perfectly functioning MacMini, 3.2 GHz 6-Core Intel Core I7, 64 GB 2667 MHz DDR4, with an external ViewSonic VA2759-smh monitor. This monitor is now discontinued, purchased in 2019, and no new firmware is available for it by ViewSonic, but the monitor had been fully recognized by my Mac mini upon restart from sleep, under macOS Monterey 12.2.x, so it seems as if 12.3 was not actually ready for RC (release candidate) status when it was pushed out to the masses, not if perfectly functional monitors on still supported Mac mini platforms are rendered faulty! Please pardon my frustrated tone about this matter.

I am curious when we can expect 12.3.1? to remedy this obvious external monitor issue; or will I be forced to find a new monitor

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Answer 9

Mar 31, 2022 2:38 PM in response to tbirdvet

I use a SMK Link dongle for power (and ethernet). After today's update it wouldn't even detect the dongle (so no power) so then the external monitor (which plugs directly into the Air) wasn't detected either. I unplugged and plugged the dongle in a dozen times, reset PRAM (held power button for seven seconds, but I don't think it doesn't anything on an M1). Eventually the dongle was detected and got power to the Mac and then the monitor was detected. But not idea if this will happen again.

So my first attempt after the update made things worse

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