Some Mac users are reporting that they have run into issues with using external monitors after updating their Mac to macOS Monterey 12.3. The issues range from the Mac not detecting an external display to inaccurate screen output, say posts on the Apple Support and MacRumors forums.
So far, the macOS Monterey 12.3 update has been reported to be bricking Macs that have had logic board replacements and users have also reported issues with game controllers. Now come the issues with external monitors.
Users report that some external displays connected via USB-C are no longer detected by Macs after being updated to macOS Monterey 12.3.
One user on Apple Support reports:
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.
While many users report issues with their USB-C displays, others say that HDMI connections to the Mac are also not being recognized.
Users have discussed potential workarounds. According to one MacRumors Forums user, the issue stems from macOS not recognizing a DisplayPort protocol version, which meant they had to change the version to an earlier one with poorer quality output.
I’ve solved this problem (on 2022-03-15). On my monitor (LG LCD 27 27UN880-B IPS) I’ve went into settings, and I’ve lowered the DisplayPortVersion from the default v1.4 to v1.2. As soon as I’ve lowered the monitor’s DisplayPortVersion, my Mac with OS X 12.3 has started recognizing the second display correctly. It seems that the new OS X update has issues with a DisplayPortVersion 1.4 protocol (has faster data rate, faster refresh, and stream compression). Hope this helps.
Another short-term fix that some have reported as successful, is to unplug the external display for a short time, plug it back into the Mac, and then plug the display back into a power outlet, after which it should work.
Some users have also reported problems when using two external monitors with their Mac. This issue was reported during the macOS 12.3 beta testing period. The issue appears to remain with the release of macOS 12.3 to the public.
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.
User reports from those using Apple’s new Studio Display suggest that they are not seeing these issues. They are afflicting third-party monitors, such as those offered by BenQ and LG.
We’ll update this article if a solution is published or a fix is released.