MacOS 13.4 Ventura - External Monitor no longer detected. Worked until the update to 13.4

I actually wound up resolving this by unplugging the monitor for a few minutes and then plugging it back in. It seems like the update process put the monitor into some state that it couldn't recover from - a state that simply turning the monitor off and on again with the power button doesn't help with (the power button apparently doesn't fully reset the monitor).

The monitor resumed working as normal after being unplugged for awhile. I vaguely recall having to do something similar after a previous macOS update, so maybe this issue isn't specific to Ventura.

I am using Mac Studio M1 and I had the same issue after updating to the latest MacOS Ventura 13.4.

My monitor setup: 2x Benq monitors. One connected via HDMI and one via USB-C. USB-C connection is affected.

I tried this and it worked for me.

1. Disconnect the USB-C monitor from either the monitor or Mac. Keep the HDMI monitor on.
2. Go to System Setting.
3. Go to Display.
4. Select any other resolutions. Return to your preferred resolution.
5. Re-connect the USB-C to the monitor.

This worked for me.

If you only have one monitor, I guess you have to try other connection/options. I know that HDMI works in this update.

Currently known issue: When web browser is in full screen in either monitor, the other monitor is blacked out. I think this is still unresolved. I do not know how to feedback to Apple and I don't have time for that. Hope Apple can patch it up soon.

Best Regards.

IG: nehpyh

I was just able to troubleshoot this successfully, so in case it's helpful to others, let me document my situation. First of all, I should note that I was able to use my exact hub/dock and external monitors without issue on my MacBook Pro (M1 Pro chipset) until about 2-3 months ago. I don't know what OS X version it was running at that time, but that's when I noticed that one of my USB-A devices connected to the hub (a Leopold mechanical keyboard) could no longer be detected by my computer until I connected it (via an adapter to make it USB-C) directly to the machine. Then suddenly, my other USB-A accessory (Razer Kiyo Pro webcam) and my external displays (see below for makes and models) also were no longer detected. I have since verified the failure on another hub (Anker 777 Thunderbolt Docking Station) as well as my wife's work hub (model info not available at this time, but it was a third manufacturer).

My home setup (where problems were first discovered)

• Macbook Pro (M2 Max chipset; also confirmed with M1 Pro and M2 Pro chipsets as having same problems)
• Kensington SD5700T Thunderbolt 4 hub/docking station
• 2x HP VH240a external displays (HDMI connections)
• 2x Anker HDMI-to-USB-C adapters (for the monitors, so they could use the T4/USB-C ports on the Kensington hub)
• Other USB-A peripherals mentioned above
• Apple Magic Trackpad (connected via bluetooth but charged via a USB-C port on the Kensington hub)

The setup that allowed me to successfully fix the problem

• Same Kensington hub and M2 Max Macbook Pro
• LG 27BL85U-W external display (HDMI plug)
• 1x of the Anker adapters mentioned above for the external monitor connection

I'm still not *exactly* sure what fixed it all, but the problem seemed to be that, upon plugging my hub into the Macbook Pro (via a USB-C cable), an Allow/Deny dialog was popping up saying something like "Would you like to allow this Kensington hub access to your computer?" However, on my home setup, this dialog was popping open and immediately closing itself before I could even read what it said. When I went to my local Apple Store for a Genius Bar appointment to troubleshoot it though, and used their external test monitor (the LG one I mention above), the dialog didn't auto-close for some mysterious reason. So I was able to Allow the hub on my machine and, when I got back home, it worked flawlessly with my home setup!

What is super puzzling about all of this is that I had already tested the hub at home with no monitor plugged in at all, which I assume would have triggered the Allow/Deny dialog properly, but it didn't. It's possible that the dialog won't trigger without a device attached to the hub that you're trying to connect, but I'm not sure. Ultimately, the most likely explanation to me is that my HP monitors weren't communicating through the hub in a way that Ventura/Sonoma OS X could understand to properly trigger the Allow/Deny dialog and using the LG monitor worked better.

I hope this helps those of you still struggling out there! The key takeaway: try a bunch of different external displays to see if this confirmation dialog is the real culprit. Once you Allow, you should be able to switch back to your preferred setup and have it all work again.

So it finally works! Designers need to go back and reconsidering the UX/UI.

a “tiny” modal appears to ask you to connect the external monitor! I overlooked it completely, navigated away!

Either give 2 points of entry as is, or:

1. make a bigger modal and disable navigating away
2. allow the user to give permissions to connect via the display settings.

What worked for me was toggling the Refresh rate on the monitor that was blacked out. It was set to 30 Hertz and I changed it to 60 Hertz and I was back in business! I had also done the other steps mentioned, ie the Spaces toggle and deleting the plist file. Neither worked. (Note, another weird finding was that connecting my iPad as a third screen caused the 2nd monitor that I was having trouble with to start displaying. This wasn't really a fix as I couldn't just constantly have my iPad connected. Of course, my iPad itself was blacked out...)

The solution that actually works was unplugging monitor from AC for a couple of seconds. Works on two different macbooks (M1), that previously after update stopped working. Unfortunately USB hub over usbc (along with video and power) is still flaky.

Omg, I tried everything else before finally coming across your response, thank you this worked! I pulled all of the cables out of my Macbook Air M1 and out of my monitor, then pulled the monitor plug and left it alone for a few minutes. Plugged it back in, plugged in USB-C from monitor to Macbook Air, and now I can use my external display again (LG monitor with USB-C, USB 3.0, HDMI, display port).

After upgrading to Ventura 13.4.1, I completely lost the use of my USB-C port for the monitor. My monitor kept telling me that the Macbook Air was using HDMI and to switch to HDMI, even though the cord and settings were for USB-C. Switching to HDMI mode on the monitor did not work, but switching the cable to HDMI did still work. Restarting the Macbook Air, changing display settings, changing security settings did not work at all.

This worked.

After the Ventura update, my M1 macbook pro had resolution issues with my 5K 34inch LG (connected through thunderbolt) and my Caldigit ts4 dock. At first, I thought it was the dock or the connecting cables. But unplugging the monitor and resetting it + deleting previously stored monitor display profiles on macbook, solved it.

A positive follow-up! Kudos to Mac to paying attention to user issues!

The update to Ventura 13.6 two days fixed the monitor problem as if it had never been a problem

+ it got rid of the slow startup from sleep that had been part of life since 13.2.

I wouldn't want people to think I wasn't grateful when things work. I am - thank you programmers!!

The one fix that worked for my MacBook Pro and Kensington Docking Station sd4750p (with 2 ASUS VP247 monitors) for all recent iOS updates (Ventura 13.2 and up) is downloading the DisplayLink Manager app.

https://www.synaptics.com/products/displaylink-graphics/downloads/macos

When you open the app, on their "Home" screen make sure you click "Launch automatically after login."

This was the tip that I needed to fix my problem.

I unplugged the power strip that had my MacBook Pro, External monitor, and all peripherals powered.

I disconnected my Thunderbolt docks (2).

I disconnected the HDMI from my monitor to my my Thunderbolt dock.

Then I re-plugged everything in, in the same order.

i got it working again by doing this:

delete ~/Library/Preferences/ByHost/com.apple.windowserver.display.{XXXX{.plist and restart

I was able to get my secondary monitor working again.

My current setup is a Mac Mini M1 2020 with a TwelveSouth StayGo USB-C hub. The primary monitor is using the Mac Mini's HDMI port while the secondary monitor is plugged into the USB-C hub's HDMI port.

Not sure which combination of things helped, but here's what I tried:

• I toggled the Displays Have Separate Spaces option under Settings > Desktop & Dock as suggested here: MacOS 13.4 Ventura - External Monitor no … - Apple Community
  • The option was already toggled on for me so I toggled it off, then logged out and back in. Then toggled it back on and logged out and back in again.
• I deleted the plist file and rebooted, as suggested here: https://discussions.apple.com/thread/254875167?answerId=259082968022#259082968022
• Lastly, I unplugged the USB-C connection between the StayGo hub and the Mac Mini and plugged it back in. Then I unplugged and plugged in the secondary monitor HDMI connector on the StayGo hub.
  • That brought the second monitor back online

Thank you.

I had previously tried detect displays, restarting, pulling cables, etc.

After the last restart, I re-searched the issue online and found this post. The first two didn't seem to apply but I figured wouldn't hurt trying the unplug usb-c at the (MB Pro Intel) port...

Voila, the monitor came back on and was recognized (VP2768-4K) as it has been for a long time until this issue arose yesterday (Not sure why it started yesterday 2024-01-03 for me).

TLDR:

• symptom 2 different (VP2768-4K,34UC89G)external monitors, 1 HDMI (34UC89G) 1 USB-C (VP2768-4K), but both monitors show as 34UC89G (whereas previously they were correctly detected.
• Solution (for me): restart mac, unplug then replug in the USB-C connected monitor at the mac usb-c port.

Thank god – this worked for me! I left the monitor unplugged for a few minutes, unplugged the usb-c cable as well. When I turned it back on, it all came back to normal.

Thank you :-)