macOS Sequoia 15.3 wont let me detect my second display

Before the latest update to 15.5, I was able to fix this problem by running:

sudo rm /Library/Preferences/com.apple.windowserver.displays.plist

However, this doesn't work any more. With the help of ChatGPT I used the search described elsewhere in this thread :

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

The suggestion from the AI was to run:

sudo rm -f /Library/Preferences/com.apple.windowserver.displays.plist \
  /System/Volumes/Data/Library/Preferences/com.apple.windowserver.displays.plist \
  ~/Library/Preferences/ByHost/com.apple.windowserver.displays*.plist \
  ~/Library/Containers/*/Data/Library/Preferences/ByHost/com.apple.windowserver.displays*.plist \

GPT: "Yes, it’s very likely macOS now references or prioritizes:

• /System/Volumes/Data/...
• User-scoped container directories (~/Library/Containers/...)
• Possibly multiple copies under specific ByHost UUIDs (try clearing all you find)."

Then shutdown:

sudo shutdown -r now

This worked for me. It looks like the displays.plist is now in a different location after the update, but I haven't bothered to work out exactly where yet. - This narrows it down a bit though. I hope this helps someone else, it's a really frustrating problem that has cost me a few days work over the last year.

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!

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.

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

To be constructive, after rebooting and tearing up a bunch of wiring, all with no effect, I installed an app (from the Apple app store) called "Display Menu". In my case, I could tell that the MacBook was *kind-of* seeing my external monitor (which as with everybody else here has been working for months before 15.3). I could tell this because the monitor, instead of showing the TV error about there being no HDMI signal, was showing a message clearing coming over HDMI from the mac telling me to choose the display mode (in a weird way that makes no sense). The "Displays" settings thing, the MacOS one, however did not see the monitor. With that "Display Menu" app installed, I got a little widget in the menu bar that *did* see the external monitor, and it let me choose it as an extended display. Now it works fine.

Again, I want to be clear in my opinion here (which is very important :) that this is an OS issue. Maybe Apple has some idea of a new/improved/different feature, but it does not work properly now whether it's a good idea or not.

Came across a clients 14" MacBook Pro (M3) that had this issue with a large (42" or so) curved LG Thunderbolt Display.

Followed most of the instructions below with no luck. Deleting the files mentioned below and restarting did not work as is.

What finally DID work was downloading the Display Menu app and using that to get the Mac to finally see/detected the monitor and allow me to extend the displays.

My recommendation:

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

Download (App Store) the Display Menu app. Open the menu and it should detected your screen and allow you to extend (or mirror) your display.

Director of IT - major college at a large Big10 university

This just happened to me two days ago. I thought my cable had failed, and I ordered a new one. Next day, it after the cable arrived and replacing the cable proved useless, I searched and found this thread.

I first tried moving just the more narrowly focused file at

mv /System/Volumes/Data/Users/<myusername>/Library/Preferences/ByHost/com.apple.windowserver.displays.<hexadecimal-uuid-value>.plist ~/Desktop

and rebooting, but nothing changed.

Then I moved the file at the more general /Library/Preferences location:

sudo mv /Library/Preferences/com.apple.windowserver.displays.plist ~/Desktop

and rebooted, and all is well.

What is crazy is I had run the OS update a few days prior, and had no issues when I plugged the external monitor in. It was only when I switched inputs & cables for the external monitor that the problem suddenly appeared, but even switching back to the original input and cable, the issue persisted. FWIW I'm using a USB-C to DVI cable to drive a 49" Samsung Odyssey G9 from an M3-equipped MacBook Pro; the cable I'm using allows the monitor to run at 120Hz (limit of the Mac hardware). None of that matters for this issue. But I'm including it in case doing so helps others find this post when they search.

Got hit with this upon upgrading from Sequoia 15.5 to 15.6. on an M1 iMac.

Second monitor running through a USB-C Thunderbolt to HDMI adapter refused to be recognized after the upgrade.

Logged in as a different user, no change

Did the system prefs->Displays->Hold Option Button-> auto-detect and it still wasn't recognized

Swapped USB-C Thunderbolt adapter to a different USB-C Thunderbolt port on the iMac, no change

Unplugged and reconnected all cables, no change

Deleted the relevant ~/Library/Preferences/ apple.windowserver...XXX file and rebooted, no change

What finally worked was to use a different USB-C Thunderbolt to HDMI adapter on the failed monitor, then the Mac suddenly recognized the monitor. After that, I swapped back to the original HDMI adapter that was not working and then "magically" the Mac was able to recognize the monitor again on the original HDMI adapter.

I have a feeling it has something to do with the USB subsystem and how the OS enumerates USB devices. I've seen this a lot with USB Printers attached to Macs where they will run fine for months/years and suddenly stop and the only way to get them recognized again is to plug them into a different USB Port.

After accidentally disconnecting my external display via Screen Sharing, the monitor completely stopped being detected in macOS (it didn’t even appear in system_profiler). Macbook M4 Air, Sequoia 15.6

Checking cables, ports, and resetting NVRAM/SMC didn’t help.

What fixed it:

Open Terminal and run:

sudo rm /Library/Preferences/com.apple.windowserver.displays.plist

then restart your Mac. After restarting all worked again!

Note: This deletes the global display configuration. macOS will recreate it at startup.

Hopefully this saves someone time and nerves 😊

I tried everything, and it was this that seemed to trigger the monitor being detected again for me! It started with 15.4 and persisted with 15.5. I finally got it working today by completely unplugging the thunderbolt cable, turning it around and plugging it back in again (maybe it was just fully unplugging both ends rather than turning the cable around, I'll probably never know).

For context, I have a MacBook Pro 16 (2021), plugged into a Thunderbolt 3 Anker dock via single cable to provide power and monitor connection (4K monitor is connected to the dock via HDMI). After upgrading directly from Sonoma to Sequoia 15.4 my monitor was no longer detected. I upgraded through a couple of bugfix versions, before getting 15.5 today, and still no luck. I was having to plug the monitor into my MacBrook Pro directly via HDMI in order to get some work done... until today when I tried unplugging everything (only 1 TB3 cable and 1 HDMI cable), plugged the HDMI cable back into the dock, turned the TB3 cable around, and hey presto, the monitor came back to life.

You sound desperate so I’ll report my answer so maybe you will see it.

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.

Came across a clients 14" MacBook Pro (M3) that had this issue with a large (42" or so) curved LG Thunderbolt Display. All was working OK until they updated to 15.3.1 from 15.3.

Followed most of the instructions in this thread with no luck. Deleting the files mentioned below and restarting did not work as is.

What finally DID work was downloading the Display Menu app and using that to get the Mac to finally see/detected the monitor and allow me to extend the displays.

My recommendation:

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

Download (App Store) the Display Menu app. Open the menu and it should detected your screen and allow you to extend (or mirror) your display.

Director of IT - major college at a large Big10 university

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

I can confirm this worked for me on version 15.3.1 - I have three external monitors + the MacBook Pro screen.

It may or may not make a difference, but I disconnected the monitors, deleted the file, shut down and restarted before adding each monitor one at a time.

Confirmed that this is a software issue!! Took my M1 Pro to Apple and they said it was an issue with the logic board, so they replaced it. The logic board is pretty much the entire inside of the laptop. Brought it home, loaded a fresh copy of Sonoma (previous version) that was available in the logic board (hard drive) and boom - issue was fixed.

Then I loaded my backup from Time Machine, which had the latest copy of Sequoia, and the issue reappeared. This became clear that this is a software issue.

I re-erased my laptop and started from fresh with Sonoma, waiting for Apple to announce the bug has been resolved.

I have been told by an Apple consultant that it is most likely due to corrupted code from a previous MACos versions that has carried over. So, if I were to upgrade to Sequoia starting from a fresh copy of Sonoma, I may not have the issue. Currently, I just don’t want to take that chance of reverting back, as it severely affects my productivity.