macOS Sequoia 15.3 wont let me detect my second display

This is god send! This one worked out for me and I've been having the issue for a week! Thank you so much.

Re: “To Apple, when will the second external monitor issue be fixed?”

This is a user-to-user forum. Apple largely is not here except to moderate it, and so will not see or reply to your message.

I think this is the best solution, this worked for me thanks

I was on with Apple support and we followed this process, and it did not work. Updated to 15.3.2 when it stopped working.

It was easy to just trash this file: apple.windowserver.displays.<hex_string>.plist : and restart and problem solved.

I too had the same issue. I rebooted a few times and still prevailed. I unplugged my thunderbolt hub where my displays are connected via HDMI and that still didn't work. It wasn't until when I pulled the HDMI cables and switched them that for some reason the displays detected again and all is well. Best of luck!

@geapgr - Are you saying this was a permanent solution for you? Were you experiencing this issue every time the system went into sleep mode - which is only where I am seeing it? Will of course give it a try, but sadly have just made power cycling the HDMI monitor part of the startup process. Hoping for 15.3.1 and a resolution!

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.

@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.

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.