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

UNPLUG your monitor's power cable and not just power cycle via on/off button.

This did the trick for my Dell U4021QW and it's working now in 5K 60Hz via Thunderbolt on macOS 12.3.1!

my monitor hertz limit is 160 and the new update had it configured for 165, soon as I turned that down it was fixed.

Same Issue here as well!

Mac Mini 2018 with BenQ PD3220U. Thunderbolt 3 used at both ends. Tried also HDMI.

Tried all solutions I have found here and at other sites.

Fortunately I did run a SuperDuper backup before upgrading to OS 12.3 so therefore I am now back at 12.2.1 again.

Does anyone at Apple read these cries out for help or do we have to mail bomb Apple Support?

Same issue with BenQ EW3270U and Mac mini 2018 (intel). Two solutions (after 2 useless helpdesk-sessions and 2 re-installations):

1st Changing from USB-C to HDMI. Works instandly, but no sound from monitor.

2nd Turning the USB-C plug 180°. Works perfect.

Maybe a workaround, but not for free. Today bought a ANKER PowerExpand+ 7-in-1 USB-C PD Media Hub EUR 31,99 from Amazon.

It works with HDMI cable. Max resolution 3200x1800. Not the best, but it's more comfortable to work.

Nevertheless, I expect Apple to fix this bug immediately. If this takes a long time, the question arises of clarifying this in court.

Unnecessary investment in cables and adapters, massive limitations in daily work.

Update. Called support again as the adapter they kindly sent did not solve the issue. Today after a good 45 minutes of troubleshooting the tech asked if I had factory reset the monitor after the update 3.1. I had not so we gave that a try. SO FAR SO GOOD! I will work the day and see how it goes but so far it has been working normally. I am using a Lepow Z1 portable monitor connected via usb-c to usb-c with MacBook Pro 2019. If you have not factory reset you might give it a go.

Keep:

• Contacting Apple Support and open tickets
• Indicate "I have this question too" on the top post of this thread

Try:

• Reboot
• Unplug power cord from monitor (not just a power button/switch)
• Different USB-C cable
• All different USB-C ports

You could also try the public beta of macOS 12.4 and see if that makes a difference.

Yes, please everyone contact support. The techs I have spoken with have not yet taken any of these calls. Also, one more thing to try, my monitor finally started working today after I did a factory reset on the monitor. So far, with half a day of work it has steadily worked properly.

Give this a try:

preconditions: MAC is off. Monitor is off and power is unplugged.

• Connect the monitor into the MAC via Thunderbolt cable
• Plug in the monitor into power
• Switch on the monitor on with the usual power button on the monitor
• Switch on the MAC (press the power button)
• login to the MAC
• Unplug the monitor from power (without switching it off), meaning just unplug the power cable.
• Wait a few seconds
• Plug in the monitor back into power. Remember the monitor is still switched on. So you should see now the usual small power-on light on the monitor
• Check the MAC now if its connected to the monitor now.

Hey everyone, this issue has been plaguing me as well for months, I was on 12.0.1 until like June and decided “I never upgrade what could they possibly break?”

I didn’t see this mentioned, but I found that the “most convenient” fix doesn’t require unplugged and plugging in cables at all. Simply go to the display settings, and change your resolution. For me my 1080p Asus monitor I drop down to 720p, the screen turns on and then just click back to the resolution you want and it should work in that resolution. If you let the display fall asleep though you will need to do this again.

I restarted my USB hub and now it's ok.

Same setup as you, and setting the DP version back to 1.4 on the monitor fixed the issue for me.

I finally got both monitors to work. I finally shut down (not restart) my Mac mini 2018 and waited for a few moments and then both monitors worked. I will see if they continue to work!

I eventually downgraded to 12.3 and it works for me now. Apparently, 12.3.1 has a problem on display.

Also happened to me with Apple HD 30" in a Mac Pro. When updated to Monterey, went blank. The problem is the USB-A . If you disconnect it the monitor works.