Some Macs not detecting external displays correctly after updating to macOS 12.3

If you’re having problems with Mac displays, you’re not alone—Apple’s macOS Monterey 12.3 update is in fact causing a range of issues with external monitors.

macOS Monterey featured image
  • Some people are reporting problems with external displays connected to their Mac after installing Apple’s latest macOS Monterey 12.3 software on their Macs.
  • It’s unclear how widespread the problem is, but the reported issues range from the monitor not being recognized at all to flickering and switching to an incompatible signal, and beyond. There’s a workaround, however.
  • If you use your desktop Mac with an external display connected, it may be a good idea to skip updating to macOS 12.3 until Apple delivers an official fix.

External display issues on macOS 12.3? You’re not alone.

User complaints published on Apple’s own support forums confirm several issues, from Macs not detecting displays at all to Macs switching to inaccurate screen output. One customer wrote on Apple’s forums that their USB-C monitor no longer displays an image after updating to macOS 12.3. All monitor brands appear to be affected by this software glitch except for Apple’s own Studio Display.

We tested this by installing macOS Monterey 12.3 on a Mac connected to Apple’s discontinued Thunderbolt Display. Not only has it worked fine after the update, but we even saw fewer issues with our Mac not turning on the monitor than normally. It’s unclear whether the problem only affects USB-C displays. Some folks have confirmed that the problem persists even when the monitor uses an HDMI connection. Read: Troubleshooting tips for fixing external display issues on your Mac

Sami Fathi, MacRumors:

Other users have shared similar experiences. While many also report issues with USB-C displays, others also say that HDMI connections to the Mac are not being recognized. Some users have been able to crowdsource potential workarounds in the meantime. According to one user on the MacRumors forums, 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.

So how can you alleviate the problem?

What can you do about this situation?

If you’re affected by this issue, you may see a “no signal” message or some such on your external display. A workaround solution is to unplug the display for a few seconds before reconnecting it to the computer and then plugging the display back into a power outlet. Doing so may temporarily squish this nasty bug until it raises its ugly head again. Read: How to manage settings for external displays on macOS

Affected customers could also try rolling back to the previous macOS version, provided they have created a full backup before installing the update. But doing so may not be worth your time because even though Apple hasn’t acknowledged the problem, it’s surely working on a fix that may arrive sooner than later. As an alternative approach, try using a different USB-C cable or connection type (i.e. Thunderbolt or HDMI) and see if that helps.

This isn’t the only problem affecting macOS Monterey 12.3. We reported about other issues that some folks have been complaining about after installing the latest Mac update, including problems with using game controllers, as well as endless boot loops and bricking on systems with replacement logic boards.