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

After updating my Mac Mini today to 12.3, my monitor now no longer displays an image via USB-C, just keeps saying on no signal on the monitor.

I have tried HDMI and same issue. The odd occasion it will display a picture but once I shutdown or restart the mac mini it does not display a picture. The mac is booting up. I have had to resort to connecting it to my old TV with HDMI connection.

This is so frustrating

I have tried resetting the SMC which had not appeared to work, also tried downgrading the displayport version from 1.4 to 1.2 (on the odd occasion I did get a picture) but that has not worked either.

Has anyone else having this issue?

The monitor I use is a BenQ SW270C.

This is really doing my head in and was wondering if anyone else has got a fix to this.

[Re-Titled by Moderator]

Mac mini, macOS 12.2

Posted on Mar 17, 2022 12:48 PM

Top-ranking reply

astn

Level 1

9 points

Posted on Mar 18, 2022 11:30 AM

So this is related to a previous long-standing bug with DisplayPort, which forced all of us to go into our monitor settings and switch from DP1.4 to DP1.2 so our external monitors would work. Apparently in "fixing" this bug, Apple decided that checking autonegotiation was redundant and the user needs to manually fix things.

The solution is to set your monitor to DP1.4. For a BenQ monitor, that is going to suck, because if you don't have a valid source input, it won't give you the display settings menu. You'll need to hook up a second computer to the monitor without macOS 12.3 so the monitor has a signal, then go into the menus (System -> Advanced -> DisplayPort) and switch back to DP 1.4. Your monitors will work.

I'm so happy to have had to troubleshoot this in the middle of a workday. It was problems like this that caused me to switch from Windows to Mac over twenty years ago.

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

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