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I'm trying to connect a MacBook Pro 16" to my external display through DisplayPort with these devices :

But it's not working.

When I plug it in, the external display goes out of sleeping mode, but the MBP does not detect it and after a couple of seconds, the display displays a "no input detected" message and goes back to sleep.

I've tried :

  • Reseting the SMC and NVRAM and tried all 4 usb slots.
  • Switching off and unplugged the display, plugged it back in etc.
  • Restarting in clamshell
  • Force detect the display (the display goes out of sleeping mode, but then wont be detected)

I've tested the cable, adapter and screen with another computer and everything works fine.

Is there something I'm missing here ? Is it possible that my external display isn't compatible ?

== Edit ==

It looks like incompatibility between MacOS and this iiyama model (or I guess this DisplayPort version).

It also seems to be a software problem, since it works under Windows/Bootcamp (!)

I've raised the issue to the Apple support, but of course no answer, and I think no hope of this getting solved.

Basically, I need to buy a new screen... sad.

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  • Just because it works on another computer doesn't mean it will work on a Mac. Macs, annoyingly enough, can be a bit picky with hardware. I'd start with a different brand adapter and go from there.
    – Steve Chambers
    Aug 12, 2020 at 15:28
  • This is already the second brand I'm trying :-(
    – Pierre
    Aug 14, 2020 at 9:08
  • I'm having sort of the same problem: Samsung G9 49" screen, DisplayPort to USB-C cable. Trying to connect it to a 2019 MBP 16" (the one with a physical esc-key) - nothing happens. (Tried 3 different 2019 MBP 16"). Trying to connect to an older MBP (2017 I think), and it works. Have you figured out anything?
    – Morten Berg
    Dec 9, 2020 at 19:58
  • @MortenBerg I couldn't get it to work with DisplayPort and my iiyama display (although it works with Bootcamp and my iiyama display, or with other displays with straight usb-c...). In the end, I bought a straight hdmi to usb-c adapter and it works fine (no hub, hubs with multiple ports also caused troubles when hdmi cable is too long, for far away projectors for exemple). For me, disappointing experience ! :-(
    – Pierre
    Dec 10, 2020 at 21:05
  • Yes, very disappointing :/ So strange that it works on older MBPs, but not the newest ones. Even stranger that it works on newer MBPs running Bootcamp...
    – Morten Berg
    Dec 10, 2020 at 21:41

5 Answers 5

Reset to default
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What worked for me was to go to my monitor settings, where I could change the version of DisplayPort signal from 1.2 to 1.1. After that, my USB-C to DisplayPort cable works as just fine, without lag and in all resolutions (up to 4K).

Background:

When I tried to hook up my AOC 4K monitor, I first tried it through my Lenovo Thinkpad Dock. For this to work on the Mac, I needed to install DisplayLink software, but for the 4K monitor, this causes lag because of CPU spikes when the graphics card needs to do stuff.

I tried both USB-C to HDMI as well as USB-C to DisplayPort cables, which both gave the issue that the monitor would show up for a couple of seconds after the signal dropped again. I was reading up on compatibility, but I couldn't really figure out what was going on. I knew the cables were alright and the monitors would work fine with Windows and through the DisplayLink (via the Dock). I read people would alter some monitor settings, I didn't expect much but luckily my monitor allowed me to swap the DisplayPort version. Not sure if either my computer couldn't handle the DisplayPort 1.2 or the cable.

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2

You just need a simple Type C DisplayPort cable.

The confusion comes from how “USB-C” was implemented. USB-C is just the physical port type. The ports on your MacBook Pro are actually Thunderbolt 3 ports and they use a Type C connector. Thunderbolt has several signals: PCIe, USB 3.x, DisplayPort and Power.

So, that port is natively outputting DisplayPort and the adapter you purchased is an actual video adapter that connects to USB and outputs DisplayPort. It’s not working because your Mac doesn’t have the drivers for that particular adapter.

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5
  • I just bought a cable instead, let's see if it works then, thanks!
    – Pierre
    Aug 14, 2020 at 9:08
  • I received the cable (I bought the CableMatters mentioned in the question you linked to) but I still have the same problem. The behaviour is exactly the same as with the adaptor... :-( So I think it might be a compatibility problem between my eternal display and the MPB 16"
    – Pierre
    Aug 17, 2020 at 16:05
  • What's your display make/model? Can you try a different monitor?
    – Allan
    Aug 17, 2020 at 16:09
  • I listed the screen model in my question. I will try to find another display to test on yes... This is annoying me a lot :-)
    – Pierre
    Aug 18, 2020 at 8:26
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    Update... I've tried with BootCamp... And it works fine, so it seems that it's MacOS related and not an hardware issue. Damn... it's working with Windows but not MacOS... And for info, it works with cable AND the DP/USB-C adapter
    – Pierre
    Aug 18, 2020 at 9:13
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This might not be the solution for everyone, but it may save someone some frustration:

Your Macbook's power adapter must be plugged in or it simply won't recognize that you've connected an external monitor.

This is at least true of the 16" Intel MBP on macOS Monterey and it could very likely be true for other configurations.

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  • Thanks for sharing, it does not apply to my case though. It works for me on battery power with hdmi (with this specific screen I'm having problem with).
    – Pierre
    Feb 10, 2022 at 8:50
  • I appreciated the suggestion also, but had no luck there either. I connected the MagSafe power cord to my Macbook Pro 16". Then plugged my Keystone USB-C docking station in and the monitors were still not recognized.
    – benhorgen
    Mar 16, 2022 at 3:43
1

Actually, I found on a 2019 MBP 16" that when the integrated (Intel) graphics are enabled (default, if computer is running just idle after start) then it may not detect a display on usb-c / displayport.

I solved it by installing gfxcardstatus ( https://gfx.io/ ) and switchted to discrete graphics, re-plugged and it worked.

Yet, in theory, you should be able to run some software that auto-switches to discrete graphics (e.g. Photoshop) and unplug / plug should work as well. Haven't tried but I assume this may do the job.

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This solution may not solve the issue for everyone: I am using the very same cable and I had a similar problem with a Dell monitor. The problem was the monitor, and not the Mac.

What I did was resetting the monitor, in my case I had to basically unplug and press the monitor's power button for at least 10 seconds or more.

After that, the Mac immediately recognised the monitor and connection was established.

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