I recently updated my MacBook Pro 14” (M2) to macOS Tahoe. Since the update, my external display is not being detected when connected via HDMI. However, if I connect my iPad as an external display, both the iPad and the external monitor work. Once the iPad is disconnected, the external display also stops working.
[Re-Titled by Moderator]
Original Title: Tahoe external display not detected
MacBook Pro 14″, macOS 26.0
macOS has become progressively less tolerant of video data packet loss due to sub-par cables. There have been several reports of setups that worked in Sequoia not working in Tahoe, with nothing changed but macOS.
Best recommendation at this point is to try a new cable. Be sure to high quality cables (HDMI should be labeled Ultra or Premium, USB-C cables should be rated for high-speed data transfer), and cables should be as short as possible (≤1 m, ideally...for Thunderbolt 5, ≤0.5 m). A random cable you found in a drawer might or might not work.
I have a high quality USB C cable, and new 38 inch LG monitor I've been using with my macbook pro 2024 14" model. I've just upgraded to MacOS Tahoe, and now my macbook doesn't recognise my USB-C monitor when plugged in. It was working flawlessly before the upgrade. Extremely frustrating!
Not just external display. Cannot connect any of my midi devices either. In practise this all rendered my Mac useless. Losing thousands because of this as I needed to turn down work. Shame.
I guess the only way is to save anything important like all my music projects to external hard drive / pen drive and try to wipe everything clean + make fresh install. That will be nice few days.
Complete mock up. Shame on you Apple.
I also experience the originally described issue. (I deeply regret installing Tahoe so early. This is by far not the only...)
veronyka98's solution worked once for me. But after stopping the mirroring for one window, all mirroring stopped. And now the MacBook does not show any indication of the external display being connected anymore. Even running through those commands again doesn't bring any mirroring back.
[Edited by Moderator]
Tried the terminal commands to no avail. The problem is that it sometimes works. Tried on two different monitors. Seems to have a long delay and then it might come on. Othertimes, it comes on right away. I'm surprised there isn't an upgrade fix to this yet...will try ordering some new cables next, I suppose.
<< SD5000T5 EQ Thunderbolt™ 5 dock.
all paired with premium StarTech USB-C cables. >>
The lead-in cable for that Thunderbolt-5 dock must be a genuine Thunderbolt-5 cable no longer than 0.5 meters. if those USB-C cables are used as lead-in cables (between Mac and Dock) you will lose most capabilities of those docks.
if you are using USB-C cables to your displays, they are limited to ONE meter, maximum.
Thank you. This was driving me crazy after the recent Tahoe update and this fixed me right up!
I have Time machine set for all of my Macs. Just never needed to use them before :D
Thank you so much! I was about to roll back to the previous version of the OS, that would’ve been a hassle.
Thank you for this!! Fixed for me too, finally, after these steps.
Apple just (November 3, 2025) released macOS Tahoe 26.1. We'll see soon enough if the update fixes the problem.
This worked for me. I only had to the first and third commands though.
Did the job for me (for now), thank you very much!
Many, many thanks for posting this - it worked perfectly!! So relieved it is working and so grateful you posted the fix. Have a great holiday!
External display not detected after macOS Tahoe update via HDMI
