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I'm having a rather annoying issue with my MacBook Pro 16" 2019 device since upgrading to macOS Big Sur. Every time I plug my device to my 4K monitor into the device (via USB-C to USB-C, or USB-C to DisplayPort), macOS will show a maximum resolution of 1600x900 but my monitor's recommended resolution is 3840 x 2160.

Photo shows the Display setting screen, with resolution of 1080p selected

I currently have a workaround to resolve the issue which is the following:

  1. I switch from 1080p resolution to 1600x900
  2. Un-plug the cable, and plug it back in again
  3. Then switch to 3840x2160

This process can be tedious and take a while to complete (between switching resolutions). Is there any solutions which people are aware of?

These are the details of the device and monitor

  • macOS Version: 11.2.3
  • Model: MacBook Pro (16-inch, 2019)
  • Processor: 2.3 GHz 8-Core Intel Core i9
  • Graphics: AMD Radeon Pro 5500M 4GB
  • Monitor: BenQ EW327OU

These are the things which I've done to date

  • I can't pin the issue on the monitor, as I've been using a MacBook Pro (2017) with the monitor for a week or so without a single problem.
  • Used ColorSync to repair any issues with the monitor profiles
  • Used various other cables such as HDMI, USB-C to USB-C and USB-C to DisplayPort.
  • Reset NVRAM and SMC
  • Re-installed macOS
  • I can't reproduce the error in Windows via Bootcamp, so I'm confident it's OS related.
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2 Answers 2

Reset to default
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There is an ongoing bug with Big Sur 11.1 and 11.2 where

USB-C ports to fail to recognize external monitors, rendering external displays unusable and unable to connect. This appears to be affecting both DisplayPort and HDMI displays connected directly and through hubs and adapters.

and

The second issue results in resolution issues with external displays unable to work at a full 4K 60Hz resolution, instead locked at 30Hz. In some cases, a 4K monitor is only recognized as a 1080p monitor.

So far there doesn't seem to be a fix from Apple.

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    I'm personally screwed: I have already downloaded the last update before knowing about the bug, but haven't restarted the computer yet... I can't turn it off until a fix arrives!
    – Luciano
    Mar 25, 2021 at 18:39
  • Thanks for sharing that article - hopefully it will be resolved in a future release then! :)
    – asimplecore
    Mar 25, 2021 at 18:41
  • I can confirm that this issue is now resolved in 11.3
    – asimplecore
    May 2, 2021 at 13:41
  • @asimplecore that's great news, I'll wait a bit then update both my mac and my answer
    – Luciano
    May 3, 2021 at 8:53
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Confusingly, it does appear to be wire related. I found my original USB-C to USB-C cable which came with the monitor and it resolved the issue.

EDIT (26/03/2021): I spoke too soon. The issue has occured with this cable as well. However, as noted by Luciano, it appears to be a known bug by Apple and will therefore be resolved in a future release.

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  • Any ideas when they might update this? I'm about to throw my laptop out the window. External monitor was working fine at 1440p: I bumped the cable and now 1080p is the best I get. Rebooting and replugging hasn't helped yet.
    – TonyH
    Apr 14, 2021 at 17:28
  • I don't know of any further information on the issue. Hopefully soon though! In the meantime, try other cables - I find some cables have this issue less than others in macOS.
    – asimplecore
    Apr 15, 2021 at 12:19
  • What seems to have fixed this was reseating the DP end of the cable into monitor. Not sure why it worked, since initial problem was bumping then usb-c side.
    – TonyH
    Apr 19, 2021 at 20:43
  • Hey @TonyH - based on the change logs of Big Surr 11.3, it seems to be fixed! I haven't upgraded yet to confirm however.
    – asimplecore
    Apr 30, 2021 at 13:10
  • I've since upgraded and the issue is fully resolved for me in 11.3 (20E232)
    – asimplecore
    May 2, 2021 at 13:42

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