macOS Sequoia 15.3 wont let me detect my second display

It's very clear there is an issue with this update, the internet is full of it, already at least more than a month. No solutions worked for me. This is 100% a software issue on apple's side. I need the second screen for work and it affects my productivity a lot. When will Apple fix it?

I have a solution (I'm using 15.2 but should work in 15.3 too). After spending 40 minutes on the phone with apple, we figured out how to solve this. In the Finder, go to the "Go" menu, select "Go to folder". Type in "~/Library/Preferences" There is a preference file with the name that starts with "com.apple.windowserver.displays." then has a random long number, then ends in ".plist". Right click on this file, and "Move to Trash". Restart your computer. Done

First, I ran this command:

sudo find / -name "*windowserver*" 2>/dev/null | tee ~/Desktop/windowserver_files.txt

Then I analyzed wherever the plist files are there.

Then this

sudo rm -rf /Library/Preferences/com.apple.windowserver.*

Then I rebooted. It worked for me. I upgraded to 15.3.1 hoping it would fix the issue but it did not.

This fixed it for me.

Delete ~/Library/Preferences/ByHost/apple.windowserver.displays.<hex_string>.plist and reboot.

here's the solution. close the mac. disconnect ALL cables (all!). close the monitor or just disconnect ALL its cables. wait 5 minutes. reconnect and boot all devices. worked for me and I had the exact same problem.

This is what worked for me. I have a Mac Studio with three monitors. After the 15.3 update, only two monitors would show up. I have three different user accounts on my mac. 1) Administrator, 2) my main user account, 3) one for my son.

All three monitors came up in both my administrator user account and son’s user account. It was only my account where just two of the monitors were detected, which told me the problem was probably an errant file somewhere in my user account library.

I traced the file to library/preferences/byhost/apple.windowserver.displays.

I dragged this file to my desktop and restarted the mac. Upon rebooting, all three monitors successfully appeared.

I did have to reset the parameters of each monitor in the Display Preferences Panel eg arrangement, rotation (one of my monitors is vertical), screen size (eg 3840x2160), etc.

Hope this helps.

The disconnecting everything solution did not work for me. My monitor goes automatically into power-saving mode. It works fine when connected to a borrowed PC.

This must be joke...

External monitors are not working after the upgrade and Apple doesn't even care to give a response!

Ok I fixed it: after trying everything I could read everywhere, the solution for me was very simple and strange:

I pulled the usb-c thunderbolt cable out of my second screen, then flipped it (so the usb-c thunderbolt that was in the MacBook go into the screen, and the side that was in the screen, I put into the MacBook), and then it worked again.

I'll also list other possible solutions that worked for other people, maybe it works for you (it didn't for me):

1. Disconnect and Reconnect All Devices:

• Shut down your Mac and disconnect all peripheral devices, including your external monitor.

• Wait for about 5 minutes.

• Reconnect your external monitor and other devices, then start your Mac.

• This method has been effective for some users experiencing similar issues.  

2. Reset NVRAM/PRAM:

• Resetting the NVRAM/PRAM can sometimes resolve display-related problems.

• To do this, restart your Mac and hold down the Option, Command, P, and R keys simultaneously for about 20 seconds.

• Release the keys and allow your Mac to continue starting up.

• This process can help with various hardware-related issues.  

3. Detect Displays Manually:

• Go to the Apple menu and select “System Settings.”

• Click on “Displays” in the sidebar.

• Press and hold the Option key to reveal the “Detect Displays” button, then click it.

• This can prompt your Mac to recognize the external monitor.  

I hope one of these solutions works for you. Good luck!

I have MBP M4 Pro and two external displays. One Dell and another one portable display via type-c.

Right after macos update the second display went off. And I tried everything here, restarts, unplug, all ports etc.

It doesn't work. But Dell is working fine. Before the update, on 15.2 everything worked very well.

Just adding my voice to the chorus of infuriated customers here! Brand new iMac connected to my Apple thunderbolt display from a few years ago - it worked great until I updated to 15.3 and BOOM the display is no longer recognized. I tried connecting it to my 2023 Macbook Pro running 15.3, same results. I've tried all of the troubleshooting methods and nothing has worked. Meanwhile, a 10 year old LG monitor is recognized by my new iMac immediately via HDMI with no issues. So for now, my awesome Apple display gathers dust while my much-less-awesome old LG monitor fills in.

Ridiculous.

I used to have two external monitors connected to my Mac: one via HDMI and another via USB-C. After updating to version 15.3.1 (24D70) yesterday, macOS now only recognizes one of them. The second monitor turns on but only mirrors the first one, and I can no longer extend the display.

Re: “My question now is does Apple actually read this support network.”

This is a user to user forum. Apple largely is not here except to moderate it, and is unlikely to see reports of problems unless you contact Apple Support or submit feedback on Apple’s feedback page.

There are other users (not Apple employees) here who can help to troubleshoot causes like trying to use more displays than a given Mac supports. But if you are experiencing problems with a supported configuration, especially ones that seem to be tied to a macOS update, you need to get that information to Apple. Other users here can commiserate, but do not have access to macOS source code, etc. to fix bugs. We are as dependent on Apple as you are.

You may want to include a link to this thread or others that contain detailed problem descriptions when you contact Apple. But they’re not going to notice detailed problem reports here unless you call their attention to them.