macOS Sequoia 15.3 wont let me detect my second display

RonKabele wrote:

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.

The M1 Mac mini supports two monitors - one connected via USB-C or Thunderbolt, one connected via HDMI.

The M1 Max and M1 Ultra Mac Studios support up to five monitors.

There were no M1-series Mac Pro desktops.

With regards to MacBook Pro notebooks,

• 13" MacBook Pros with plain M1 chips support only one external monitor.
• 14" and 16" MacBook Pros with M1 Pro chips support up to two external monitors
• 14" and 16" MacBook Pros with M1 Max chips support up to four external monitors

Thanks @sgreadly

It works for me!

I've tried all of these things suggested below 10 times and nothing is working for me! Please fix it asap

Thank you very much your solution worked fine... deleted apple.windowserver.displays....in MacBook air M3 with LG 2k monitor 24qp550.

I did this but it doesn't seem to fix the issue, does anyone know an alternative fix?

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 wrestled with this problem after upgrading to 15.3.1. Was about to use Apple Support to erase 15.3.1 and go back to an older version when I stumbled on a fix after reading all the comments in this thread. The display monitor is black - but you can see it in system settings/displays. When I change the refresh rate from 75Hz to 60Hz and then wait about 5-10 seconds, the monitor comes to life. It's definitely a lower quality display, but at least it's working now. Here's a picture of what worked for me. LMK if it helps to solve your problem! Also, Apple still needs to solve this software issue as we need our external monitors to be the high definition we purchased!!

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.