Macbook Pro M1 not detecting external monitor

Question

Level 1

12 points

Macbook Pro M1 not detecting external monitor

My new 13" Macbook Pro M1was initially very troublesome to connect to my BenQ SW321C monitor, but it would connect if the Macbook was booted up and then I connected the display (necessitating reconnecting the Thunderbolt cable each time. This was on OSX 11.4. Then, it stopped connecting ever. I upgraded to 11.5.1 and it STILL will not connect.

I have tried changing cables. No effect. The Thunderbolt ports connect fine to my OWC ThunderBay 8 box with any of my cables, but nothing can make the monitor connection appear, as if the MacBook has stopped trying under any circumstance to detect the display.

I have also opened my Display preference pane and held down the 'option' key to force it to look for and detect displays, but nothing happens.

This is costing me a lot of money and aggravation. Can anyone recommend anything else? This problem seems to have been ongoing for quite some time for others.

MacBook Pro 13″, macOS 11.5

Posted on Aug 12, 2021 2:46 PM

Reply

Answer 1

Top-ranking reply

Sarge_ Author

Level 1

12 points

Aug 18, 2021 3:13 PM in response to Sarge_

In the end, the solution was to perform a factory reset of the BenQ SW321C monitor (didn't 'take' on the first attempt, but tried it a second time).

With that done, everything seems to be functioning properly. The monitor boots from startup without having to unplug it first and plug it back in after booting, and it wakes from sleep, etc.

Once the factory reset of the monitor was completed and the Macbook Pro rebooted, the MAC OS generated new com.apple.windowserver.displays.plist files in the OS and User Libraries in the proper preference folders. I suspect it only generates those files in response to successfully attaching external displays.

Reply

Answer 2

kamote0628

Community Specialist

Aug 13, 2021 10:55 AM in response to Sarge_

Hi Sarge_, We appreciate you reaching out to us. We understand that you are experiencing issues using an external display with your MacBook Pro. Are you using the same steps in the article below?

Connect a display to your Mac

Based on how you described the issue, it does seem like you are using a hub or a dock.

If this is the case, we recommend that you check if the issue persists if you connect your MacBook Pro directly to your external display.

Also, we recommend that you check if the issue persists while on safe mode. Below is an article to help guide you through the process.

How to use safe mode on your Mac

Have you had the chance to check if the issue persists on a different user account? The article below can help if you do not have any other user account to test with.

Set up users, guests, and groups on Mac

Take care!

Reply

Answer 3

Aug 18, 2021 3:24 PM in response to Sarge_

to get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, the display will not be shown as present, and no data will be sent to the display. "No signal detected" is generated by the DISPLAY, not by the Mac.

This query is only sent at certain times:

• at startup

• at wake from sleep — so momentarily sleeping and waking your Mac may work

• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go

• on invoking Option-(Detect Display) button in Displays preferences (from another display)

Reply

Answer 4

kamote0628

Community Specialist

Aug 13, 2021 2:09 PM in response to Sarge_

Sarge_,

Thank you for keeping us posted. Reinstalling macOS sounds like a great next step to further isolate the issue.

If possible, we also recommend that you try a different external display to see if the issue persists on a different display.

Please keep us posted.

Take care!

Reply

Answer 5

kamote0628

Community Specialist

Aug 14, 2021 3:43 PM in response to Sarge_

Sarge_,

Thank you for keeping us posted. We recommend that you reach out to us here so we can take a closer look into the issue: Get Support

Take care!

Reply

Answer 6

Sarge_ Author

Level 1

12 points

Aug 13, 2021 2:06 PM in response to kamote0628

I am not using a hub, although I was previously connecting to the monitor via an OWC ThunderBay 8. But it makes no difference connecting direct through the laptop. (leaving the ThunderBay 8 disconnected). I have tried three different Thunderbolt cords, makes no difference.

I have also tried creating a new user, and that didn't make any difference

I have also tried removing the com.apple.windowserver.displays.plist files from the System Library and the User Library preferences but the OS does not rebuild those plist files when they are removed. (did this with phone support help from Apple).

It was working (with issues on startup) under 11.4, and then it got more unreliable (same OS 11.4). Monitor would only be recognized when booting up with it unplugged, and then plugging it in after the OS was fully booted. So I upgraded to 11.5.1, and no change.

Next I am going to try reinstalling the OS files and see if that helps, but I am reading quite a few cases of the same problem across the internet from other people as well. Seems like an engineering problem. I'm hoping someone can find a new workaround, if not a full on repair.

Reply

Answer 7

Sarge_ Author

Level 1

12 points

Aug 14, 2021 3:31 PM in response to kamote0628

UPDATE: I purchased an Apple Brand Thunderbolt 3 cable (.8m) and no change.

I then tried wiping the entire drive and re-installing a completely new OS (11.5.2) and no change.

What's most suspicious is after doing the clean install, there was no com.apple.windowserver.plist file generated in the main library preferences folder or the user library preferences ByHost folder.

Now what?

Reply

Answer 8

Sarge_ Author

Level 1

12 points

Aug 15, 2021 9:52 PM in response to kamote0628

Phone support has submitted a data file to engineering to try to solve the problem. They take several days to respond, so I won't likely have a solution until later this week.

Reply

Macbook Pro M1 not detecting external monitor

Similar questions