macOS Sequoia 15.3 wont let me detect my second display

I have the same issue. My desktop is a 2021 IMac M1. When operating Sonoma, I had two external Dell monitors working, in addition to the main display, through a DisplayLink Plug and Display Hub. One monitor worked with a thunderbolt to HDMI cable and one worked through a HDMI to HDMI cable. No problems. Worked like a charm. Download Sequoia yesterday and monitor on HDMI to HDMI is black. "No HDMI signal...." Called Apple; spoke to less than sympathetic tech who said my problem is with the DisplayLink folks. "But," I said, "there must be something in your new OS since it worked fine in your old OS. She said, "I'm sorry." I asked if possible to switch back to old Sonoma OS. "Nope." This is very frustrating. Any help would be very much appreciated.

Servant,

Thanks. It appears Apple does monitor these inquiries, as you appear to mimic the very thing I was told yesterday when I spoke with "Support."

I'm probably betraying my ignorance of such things, but it sounds as if Apple made some changes in the Sequoia OS preventing or inhibiting a further "work around", as you put it. A few suggestions: (1) rather than making "work arounds" required, you might try "work withs"; (2) an explanation of why the old OS worked and the new one does not might go further toward customer satisfaction and understanding than an attitude of what Apple did or did not promise; and (3) pointing the finger elsewhere is never a good strategy in seeking continued patronage.

As this site appears to attest, there are a lot of customers like myself who rely on multiple screens.. I would think the good folks at Apple would look for ways to accommodate those with this need in the design of their OS, rather than prevent it.

Thanks Servant.

Retired,

I don’t work for Apple.

The M1 iMac’s Technical Specifications were readily available before you bought it.

In addition, an examination of the Technical Specifications of all Macs that use plain M1 chips shows a consistent pattern. None of them support more than two displays, total, where the built-in displays on iMacs and on Mac notebooks count towards that limit.

If the plain M1 chip only has two display generators (as all evidence suggests), there is no macOS change that Apple could make to provide more first-class hardware-supported display outputs on Macs that use that chip.

That's all great. I have an M1 Pro MacBook and it had the problem. If you read this thread, you'll see that the majority of people posting have had a MacBook setup with multiple monitors on 15.2, and the setup worked. Your argument is about the nature of the bare-metal M1 CPU, and it is correct. It is also not relevant to this conversation, for obvious reasons: if people's MacBooks supported their monitors before with their CPU native abilities, they should continue to do so under 15.3.

Pointym5 wrote:

Your argument is about the nature of the bare-metal M1 CPU, and it is correct. It is also not relevant to this conversation, for obvious reasons: if people's MacBooks supported their monitors before with their CPU native abilities, they should continue to do so under 15.3.

If the macOS 15.3 update broke the ability to drive multiple monitors in a supported way – using native hardware video output – that is indeed a serious issue. One you'd want to raise with Apple Support, not just here for other users to see.

When you raised it with them, you'd want it to be clear to them that you were having issues with native hardware video. You wouldn't want them to think that you have "the same issue" as the person who told us that they were using DisplayLink to attach two external displays to a Mac that only supports one. The one who wrote right here, in this thread:

"I have the same issue. My desktop is a 2021 IMac M1. When operating Sonoma, I had two external Dell monitors working, in addition to the main display, through a DisplayLink Plug and Display Hub…."

My most recent comments were directed to that person.

Retired,

If you want to continue talking about DisplayLink, I would suggest that you start a new thread. This thread is now four pages long, and if most of the people here are talking about issues with driving hardware-supported displays using native video output, they don't need the distraction of an ongoing subthread about DisplayLink.

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.

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

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.

Same problem for me. I’ve tried all the fixes in this page and nothing has worked. It’s taken me 3hrs.

Thats 3hrs away from study for my final exam.

I’ve given up. Im going back to my study with the limitations of only one decent sized screen. So disappointing that Apple refused to allow us to work with more than one reasonable sized screen. Am convinced that this update & subsequent problems are all part of Apple’s need to make us do things their way.

Thanks for nothing Apple 🥺

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.