You can make a difference in the Apple Support Community!

When you sign up with your Apple ID, you can provide valuable feedback to other community members by upvoting helpful replies and User Tips.

Looks like no one’s replied in a while. To start the conversation again, simply ask a new question.

User profile for user: paulitoweb
paulitoweb Author
User level: Level 1
14 points

External USB-C monitor not recognized

Hi,

I got the this issue with I the new 2021 Macbook Pro 16” and my LG 4K ultrafine display LG 27UP850W which is not working properly with Monterey 12.0.2.


The display is not recognized with any of the USB-C port using the LG cable (USB-C Display port Alt mode) unless toggling power to the monitor, but monitor output is bad and at low refresh rate, this happen with both the lid opened and closed. 


Additionally a restart let the monitor not connected again, and finally the mac power on feature by monitor power switch is not working at all. 


All of these feature were working on my old 2019 Macbook Pro 16” on Bigsur (I have sadly sold!) 

I am surprised a brand new Macbook Pro 2021 has this issue , in apple do they test their products before sell them? I read this issue is affecting macs intel/m1 for almost an year, this is not acceptable!!! please Apple fixit it ASAP!

regards

Paolo Torrente

MacBook Pro (2020 and later)

Posted on Oct 30, 2021 11:36 PM

Reply
Question marked as Top-ranking reply
User profile for user: paulitoweb
paulitoweb Author
User level: Level 1
14 points

Posted on Nov 4, 2021 12:36 AM

In addition to what I have wrote:


The issue is: Monitor connection (connected via USB-C) is lost with Macbook restart, after a restart, the monitor (LG Ultrafine 4K 27UP850-W) display no signal.


The issue is not present with the integrated HDMI port of the 2021 Macbook Pro 16 inches (but I have bought an USB-C monitor just to use one cable connection with my Mac). The issue is not present with my "old" 2019 Macbook Pro 16 inches with MacOS BigSur


  1. Changing Thunderbolt4/USB-C doesn't help
  2. Unplugging USB device from the monitor doesn't help
  3. Changing Display Port version from 1.4 to 1.2 doesn't help


The only way to get again the signal is togling power to the monitor


The support page mentioned doesn't help unfortunately. I suspect it is bug with Monterey or in the 2021 Macbook Pro itself. The monitor works great with 2019 Macbook Pro 16 and an HP Elitebook notebook.


Hope in a solution for this issue.

regards,

Paolo


View in context

Similar questions

3 replies
Question marked as Top-ranking reply
User profile for user: paulitoweb
paulitoweb Author
User level: Level 1
14 points

Nov 4, 2021 12:36 AM in response to Sharon_419

In addition to what I have wrote:


The issue is: Monitor connection (connected via USB-C) is lost with Macbook restart, after a restart, the monitor (LG Ultrafine 4K 27UP850-W) display no signal.


The issue is not present with the integrated HDMI port of the 2021 Macbook Pro 16 inches (but I have bought an USB-C monitor just to use one cable connection with my Mac). The issue is not present with my "old" 2019 Macbook Pro 16 inches with MacOS BigSur


  1. Changing Thunderbolt4/USB-C doesn't help
  2. Unplugging USB device from the monitor doesn't help
  3. Changing Display Port version from 1.4 to 1.2 doesn't help


The only way to get again the signal is togling power to the monitor


The support page mentioned doesn't help unfortunately. I suspect it is bug with Monterey or in the 2021 Macbook Pro itself. The monitor works great with 2019 Macbook Pro 16 and an HP Elitebook notebook.


Hope in a solution for this issue.

regards,

Paolo


Reply

External USB-C monitor not recognized

Welcome to Apple Support Community
A forum where Apple customers help each other with their products. Get started with your Apple Account.
Learn more Sign up