External Monitor Issue After macOS Sequoia 15.1.1 Update

Hi everyone,

After updating my MacBook Air M2 to macOS Sequoia 15.1.1, I’ve encountered an issue with my external monitor. I connect my ViewSonic monitor via an HDMI-to-Type-C cable. The monitor works for about 5 seconds after being connected, then the screen goes black.

Interestingly, the monitor is still detected in the display settings, and I can even move the cursor into the display area—but nothing is visible on the screen.

Here’s what I’ve tried so far without success:

Adjusting the resolution and refresh rate.
Booting in Safe Mode.
Resetting display profiles.
Rebooting the system.

To rule out hardware issues, I tested the same setup on my MacBook Air M1. Before the update to macOS Sequoia 15.1.1, it worked perfectly. After updating, the same problem occurred.

However, I tried connecting to a Samsung external monitor, and that worked fine.

Has anyone else faced similar issues or found a solution? I’d appreciate any guidance or suggestions.

Thanks!

MacBook Air, macOS 15.1

Posted on Nov 26, 2024 8:50 AM

Top-ranking reply

MessyDuck

Level 1

14 points

Posted on Nov 27, 2024 1:43 AM

I have a similar issue. The external monitor that used to work fine prior to the update to macOS Sequoia 15.1.1 (LG 29UM69G), now flickers, i.e. goes off for about 2 seconds, then it goes back on. Happens on both my Macbook Pro M1 2021 and Mac Mini M1 2020. If I disable 'Prevent automatic sleeping when the display is off' in System settings, then my Macbook Pro goes to sleep when the flicker happens, ending any calls in the process.

This is completely random, it can work well for hours, or flicker every minute or so. I've been unable to link it to anything I do or have on my system.

Tried to change cables (USB-C, DisplayPort, HDMI), ports, screen refresh, and color profile to no avail.

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