macOS Sequoia 15.3 wont let me detect my second display

Hello everyone. This solution worked for me. I panicked when after updating to Sequoia 15.3.1 my hub stopped being detected by mi Imac M1. I use the hub for the Ethernet cable, the SD cards, a couple of USB connections for external SSD from time to time, and my second screen which I almos depend on. Try this before deleting files!

RetiredLegalBeagle wrote:

Servant

I apologize if I was rude. Thank you for your help.

I wasn't saying that you were being rude. I was suggesting that you start a new thread.

Your issue is different from that of others in this thread. Hardware-supported video and Displaylink-based video work in different ways. It is not clear whether a single Sequoia change is related to both issues – or if there were separate changes, one of which affected hardware-supported video, the other of which affected DisplayLink.

For the benefit of the people who are discussing issues with hardware-supported video in this thread, any further DisplayLink conversation should probably move to its own thread.

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

Thanks a lot, sangy987.

I was struggling with this issue ever since I upgraded to macOS Sequoia 15.1.

I'm now on Version 15.3.1 (24D70), and your solution worked perfectly for me.

My external display, the Samsung C49RG90, is now detected, and I can use the highest 5K (5120 x 1440) resolution.

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.

I believe that is the case for the M1 Mac Mini, perhaps one of the laptops. The Mac Studio M1 I have supports three monitors because that’s what I’ve been doing for over two years. But I do have a Kensington TB3 dock where two of my monitors are plugged into. I would also guess the first M1 Mac Pros support at least three or more monitors.

That solution worked for me. However, I do not believe you need to download anything. I didn’t. Since it’s a .plist, if you drag the file to your desktop and reboot, the operating system will create a new .plist file. You’ll need to go in and manually set your preferences again, though.

I waited until 15.3 because of all the reported issues with multiple monitors. For me, at least, there are still issues with 15.3. I have a MBP16 with 2 Apple Thunderbolt Monitors.

Both monitors work for me.

HOWEVER, I have to reboot every morning to get both monitors to work. When waking up from sleep, only one of the Thunderbolt monitors is recognized. Restart MBP and back to both Thunderbolts working. A pain but at least they work.

Running 15.3.2 here and the nothing has fixed this for me. I have tried all of the suggestions in this thread and none of them work for me. It definitely came with the 15.x releases and I suspect only Apple can actually provide the fix going forward. Just unfortunately has not been in the two updates released to dae.

"Luckily" for me simply power cycling my monitor wakes up this display until the next time it goes to sleep. It continues to be aggravating to say the least.

I tried this. It allowed my monitors to connect and be detected, but my MacBook Pro (M2 Pro Chip) will not detect power from the Thunderbolt. I deleted the file you described, but I have to plug in a power source, in addition to the Thunderbolt, in order to run multiple displays with the laptop closed.

Hello Magic,

When you say:

"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."

Where did you move it to? Desktop - trash - etc?

Also not sure you have the answer but, I don't seem to have that particular file in the location that has been pointed out. When I was on with Apple Support, the team member had to send it to me, then I had to delete it (lol) as per all the other outlines that refer to this particular file.

Do you have any insight on that, or anyone else reading this for that matter.

My system

14-Core CPU

20-Core GPU

48GB Unified Memory

1TB SSD Storage¹

16-core Neural Engine

16-inch Liquid Retina XDR display²

Three Thunderbolt 5 ports, HDMI port, SDXC card slot, headphone jack, MagSafe 3 port

Magic Keyboard with Touch ID

Force Touch trackpad

140W USB-C Power Adapter

Sequoia 15.3.2 (this was the update. I'm not exactly sure what it was shipped with)

It's brand new only I've only had it a week.

Thanks

It appears for me at least that the 15.4 release has resolved the issue - or at least three times my monitor has come back on its own. I tried ALL of the other "fixes" and none of them worked for me. Hoping I have not just cursed myself.

If you get to the point where the Mac is putting up that "Choice" display, then you're almost done. That tells you that the computer does know the monitor is there. This is the point at which that "Display Menu" app might help. It's free, and as far as I know it is not evil and it did help me. I installed it and it made telling the machine what I wanted easy.

Latest Update: I spent quite a bit of time today reading through this forum, documenting and trying different fixes, to no avail. I decided to go the Apple Support route so at least it would be documented with them, since I've been told they don't check this community or the posts.

After waiting for a while, I was connected with a support tech and we tried restarting in "Safe Mode" (i.e. hold the Shift key when restarting my Mac Mini M1) and that did nothing to help the situation. I'm on their schedule for a call tomorrow (Saturday) morning at 9:15 to continue troubleshooting.

Fortunately, I have my iPad to chat with Support while we are trying to make changes to my Mac Mini. I just hope a good night's sleep (for me) and documenting what they tell me to do will help convince them the update (Sequoia 15.4, installed a few days ago) is the source of the problem). I'll try to document what they tell me, and will report back what the end result is.

Wish me luck!