macOS Sequoia 15.3 wont let me detect my second display

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.

@sgreadly

Unfortunately didn't work for me.

Update to my message earlier.

My portable display worked via Type-C, everything by a single wire, power and picture.

This display also has hdmi port. And I've connected hdmi cable to my mbp and it started to work. But I had to keep Type-C as power supplier. So now I have working display, connected with two cables.

Still waiting for the OS update to solve this.

Having a similar issue. After the update my m4 mac cannot recognize my LG c3 tv. My tv recognizes the mac (the hdmi port says "apple" for the hdmi detection) but mac cannot recognize the TV as a display. the "detect displays" trick did not work nor did deleting the plist

I have also tried multiple HDMI cables. Although - the cables i had been using worked fine until the update completed...

The best I can get is -- sometimes -- the monitor displays "choose to mirror or extend display from the [ ] menu. but the TV still does not appear as a display

this is very frustrating. i have tried plugging it in directly and via a dongle

I updated my M1 to 15.3 and it still works fine with the LG tv...

I had the same problem and thought my second Apple 27" Tb screen connected to a M2 Mac mini had died, but just to check, I connected it to another M1 Mac (MBA) and it came good instantly and then reconnecting to the M2 MM worked too.

YMMV but it seems to me that somehow Sequoia can disable a second Tb screen which then requires a reset on a different Mac. This is the third time it's happened to my dual Tb screens and a "reset" on another Mac has worked every time.

The “can’t run a portable display off the Mac, with one cable, and no separate power source for the display” thing involves a different issue (or set of issues( than what other people seem to be talking about in this thread.

I have tried all of the various "fixes" as well, but nothing has worked for me. It clearly is in Apples court to get this fixed as it was definitely 15.3 that broke it. Was hopeful that would come in 15.3.1 but unfortunately it did not. Maybe we get lucky in 15.3.2.

It is VERY AGGRAVATING to have to cycle monitors ever time I sit down at the machine to work!

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.

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. 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