I have a MacBook Pro (M4) connected to an external monitor via a USB-C to USB-C cable. It was working fine until I upgraded the OS to macOS 26 earlier today. However, the external monitor is no longer detected, even after I restarted the MacBook Pro.
MacBook Pro 14″, macOS 26.0
Hey everyone, I've also just experienced this issue after upgrading to macOS 26. So a few things. I am nearly certain this is not due to the cable. Everything was working as it should before the upgrade. The issue appears to occur with USB-C connected monitors, particularly when using a docking station.
Here's how I reproduce the issue. When I use my Mabook in clamshell mode, it functions as expected. Now, if I unplug the dock and then use the laptop with nothing else connected, it works. But when I replug the Dock into the computer, that's where I get issues.
A few things I've tested: unplugging and replugging the monitors - no go.
Unplugging the Dock and replugging that in, no go. Plugging in the USB-C monitor directly to my MacBook Pro M1 Max, and still no go.
** In that Dock, I have an external USB HD connected, as well as other USB components, and if the monitors don't come into play, the drives do not show up either, so nothing is recongnized.
A few things that work, and a tentative solution until Apple resolves this issue. Plugging the monitor directly into the MacBook Pro M1's HDMI port works flawlessly. Additionally, for me, rebooting the Mac resolves the issue until I perform the above step, which is unplugging, which I do because I work at different locations.
I'm not an Engineer, nor do I play one on the Internet, but somehow the signal that checks if something is connected to USB after waking from sleep has a hiccup in it. The issue only occurs when I remove the USB-C cable, use the computer, and then reinsert it into the system.
Oh, before someone asks, I've tried all three of the USB-C connectors on my MacBook Pro. I've tried it without the Dock, and I have also tried it with other monitors I have connected to my other Mac in my home office. This issue occurs only on my MacBook Pro and only when I switch from clamshell (or open) mode to using only the laptop screen, then back to the external monitors. (And as I said, my bandaid fix is to reboot, but what a pain in the you know where)
Now that I can reproduce it, I'm writing up a bug report for Apple. Good luck, everyone!
For now I have to use a separate HDMI cable to connect to the external monitor, which was detected properly.
[Edited by Moderator]
I have the same issue. Same scenario, M4 MacBook. USB-C to USB-C 4K monitor that worked before macOS 26 upgrade. After upgrading, the USB-C provides power, so it is connected. If I use an HDMI to USB-C cable, the monitor works, but the cable does not provide power. Are there any other ideas besides the ones in the previous posts?
Just to add to the case to possibly help the devs work on a solution.
External display connected to my M1 Max MacBook Pro using the HDMI port, HDMI to HDMI, was working fine.
Until, I clicked the annoying screen button on the top right ( the one that make me feel like someone is watching my screen even though its just my own computer sharing display to my own display in front of me ), and I tapped on "Stop Extending"
This was it, there was now no way of making the screen extend to the monitor, the Mac refused to see it anymore, restarts, unplug and plug back in, different HDMI cables, nothing. Have had to resort to a usb c dongle for now, but I hope a fix comes about because this is weird.
<< Plugging in my MagSafe charger appears to completely break high speed thunderbolt connectivity. >>
That WavLink Dock is a USB-C dock, not a ThunderBolt dock, according to the maker's user manual.
Compatible with Type-C USB 3.1 Gen2 full specification PC/laptop
They appear to be using a symbol similar to a ThunderBolt symbol (genuine ThunderBolt has an arrow on the tip of the lower end) to indicate that port can supply up to 100 Watts power to your Mac. There is no claim in the specifications that the WavLink dock is a ThunderBolt device.
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If this is a Bug, it is a Bug with multiple charging methods, not Thunderbolt protocols.
I have 2 Macbooks, the one with 26 and the other I have upgraded to 26.0.1 before upgrading the external monitor worked but not after the upgrade. whereas the other mac where i still have 26, the external monitor works. so it's clearly the upgrade 26.0.1 which broke the display
what Processor type? {M-series (plain), PRO, MAX, ULTRA}
what make&model display?
What cables, adapters and docks are being used to make the connection?
Hello, I may be experiencing a similar issue. I have used a TV for my display for ages and after updating to macOS 26 yesterday, the screen is blank. When I plug the same exact cord into a computer monitor, it displays properly. So maybe there is an issue relating to using a TV as a display?
My computer is a Mac Studio M1 Max, my TV is a Vizio 65", cables are HDMI [regular?], and I am going through an Onkyo audio receiver.
As with the OP, this same setup was working fine before upgrading yesterday, and still works fine when plugged into a computer monitor instead of my TV.
To get the attention you deserve, PLEASE start a NEW discussion.
If you did not immediately find your solution by reading through the existing postings, you likely do not have "exactly the same problem" and need to explain from the beginning. This discussion is already too complicated.
Starting a new discussion will allow Readers to think hard about your exact situation and address the exact circumstances you are facing.
https://discussions.apple.com/post/question
The external monitor was not shown up in the system information (Graphics/Displays).
[Edited by Moderator]
Before the upgrade to macOS 26, the external monitor was connected (via USB-C) as an extended display and it was working fine.
HDMI cables you want for HDMI-only Displays (higher resolutions than 720p TV sets) are marked as Certified with an anti-counterfeiting tag and are labeled:
"PREMIUM High Speed HDMI cable" or that + "with Ethernet" (up to 4K at 30Hz) --OR--
“ULTRA High Speed HDMI cable" or that + "48G" (supports higher resolutions and backward-compatible)
Cables with No Certification tags are good for your standard 720p TV set, and not much more.
HDMI was invented for HD TV sets. it works great at its original resolution of 720i or 720p. At higher resolutions, it quickly develops issues that are complex to solve, and the cables and adapters required to solve are NOT intuitive.
I don't understand the logic behind recommending that the cable is the issue. The cable worked moments before I did the macOS 26 upgrade, with the same computer, monitor, and cable. Once the software was updated, the setup didn't work. This thread has many views compared to all other Tahoe topics, likely meaning others are searching for this same issue.
The USB-C to USB-C cable I was using came with a monitor. I also tried a USB-C cable that comes with other Apple products. Both have the same result.
I will try to order a Thunderbolt cable. If that solves the issue, I will report back. However, it's silly that a software update now requires purchasing a different type of cable.
<< the Mac refused to see it anymore, restarts, unplug and plug back in, different HDMI cables, nothing. >>
Using a different cable is a fix for BROKEN cables. It does nothing to improve a sub-par cable into an acceptably-good working cable.
Cables "found" behind your TV set are not likely to be high enough spec to be usable for a modern display connected to a modern Mac.
HDMI cables you want for HDMI-only Displays (higher resolutions than 720p TV sets) are marked as Certified with an anti-counterfeiting tag and are labeled:
"PREMIUM High Speed HDMI cable" or that + "with Ethernet" (up to 4K at 30Hz) --OR--
“ULTRA High Speed HDMI cable" or that + "48G" (supports higher resolutions and backward-compatible)
Cables with No Certification tags are good for your standard 720p TV set, and not much more.
HDMI was invented for HD TV sets. it works great at its original resolution of 720i or 720p. At higher resolutions, it quickly develops issues that are complex to solve, and the cables and adapters required to solve are NOT intuitive.
I have the same issue. My external Monitor hardly gets detected. It randomly works when I try like 20 Minutes or so. But if I lock my MacBook and the Monitor switches into power saving mode it won´t be detected afterwards. This is pretty annoying and started when I updated to macOS 26 Tahoe. I tried different Thunderbolt cables, turning on and off the monitor and MacBook and tried to "detect displays" in system settings.
What's kind of weird is that if the Monitor is connected and is waiting for a video signal I can use the connected devices like keyboard and mouse. So the only problem is the video signal.
<< I have a WD19TB and a WD22TB4 dock. >>
Both of those Dell docks claim support for Windows 10, Window, 11, Ubuntu, and ChromeOS. There is no mention that they intended them to work with a Mac of any description.
The checklists for both of those Dell docks suggest that if you have a problem you should update the Dock firmware. Support for that firmware update process is only provided for Windows.
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I think your recognition issue could be caused by lack of generality in the Dell firmware. "Works with Windows, that's good enough" rather than "Works with ThunderBolt across all makers of ThunderBolt hosts."
External Monitor Not Detected After macOS 26 Upgrade
