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MacBook Pro (15-inch, 2016) with 2 USB-C to HDMI adapters. The setup works great if I start up in that configuration.

If I connect the adapters while the machine is running or simply sleeping, one of the monitors will never get a signal and stay in low power mode. The OS sees the monitor, it shows in the display arrangement settings and I can move the mouse into it, but until I restart, I can't see anything on it.

Once I have restarted I can let the machine sleep or whatever, and the display still works unless I disconnect the adapter. As soon as I do that a restart is required to use it again.

Using MacOS Sierra (10.12.4)

Using this adapter: https://www.amazon.com/gp/product/B01IUXA9YK/

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  • Are you using Apple's adapter or a third party one? If it's third party, which brand and model?
    – NoahL
    Commented Apr 22, 2017 at 4:34
  • In addition to answering @NoahL 's questions, can you clarify which exact model of 2016 MBP you have?
    – Monomeeth ♦
    Commented Apr 22, 2017 at 5:47
  • Just to add a real-life experience: I'm using 2 USB-C to DisplayPort adapters (which are basically similar to the HDMI adapters) - and this works without any problems in that regard. Several times a week I plugin in both monitors after the MacBook Pro is booted (basically I never turn it off) - removing the cables again also never give problems.
    – jksoegaard
    Commented Apr 22, 2017 at 8:24
  • What monitor are you using? Does it have ports other than HDMI?
    – Allan
    Commented Apr 27, 2017 at 0:15

3 Answers 3

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The video signal on the Thunderbolt connection on your MBP is actually Display Port so you are actually going from Display Port to HDMI. I am not a fan of converting signals because it's flaky at best.

If you must connect to HDMI, try an active1 adapter like the TRENDnet USB-C to HDMI 4K. They have two versions - one that does 30Hz and another that does 60Hz (it's the Power Delivery version).

What is preferable, is to go from USB-C to Display Port which is actually Display Port to Display Port, so no there's conversion involved. No conversion means less points of failure.

jksoegaard's comments provides more evidence of this:

Just to add a real-life experience: I'm using 2 USB-C to DisplayPort adapters (which are basically similar to the HDMI adapters) - and this works without any problems in that regard. Several times a week I plugin in both monitors after the MacBook Pro is booted (basically I never turn it off) - removing the cables again also never give problems

1 I wrote an answer on this very topic: Passive vs. Active Adapter

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  • 1
    That link to the USB-C to Display Port adapter seems to actually go to a USB-C to Ethernet adapter product on Amazon
    – Pranay Prakash
    Commented Jun 11, 2020 at 2:15
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To the above answers, I can't use a USB-C to HDMI active adapter as Macbook pro provides only two USB-C ports. I don't know how a company like Apple comes up with a crappy design like this. I use 2x of this adapter: https://www.amazon.com/gp/product/B07NDH6DRN/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

1 HDMI works perfectly. 1 HDMI needs a restart every time to work (exactly the same problem as described in the question).

I'm running on the latest OS version: 10.14.5

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  • Wow, that crab-looking thing that they want us to use for all those missing ports is just something...
    – c00000fd
    Commented May 22, 2023 at 18:21
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Update to latest OSX version (10.12.5 (16F73)) fixed the problem.

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  • 5
    I am on 10.14.5 but this problem still exists.
    – Bunny Rabbit
    Commented Jul 10, 2019 at 5:29
  • @BunnyRabbit The problem will always exist. In my experience, macOS drivers (kexts) are much less tolerant of video signal anomalies than their Windows counterparts. It's not a knock on Apple or a kudo to Microsoft. It just is. To solve that problem, IMO, you use the hardware that works best with Macs and that's DisplayPort. They've been using since the early days with mDP ports next to Firewire Ports. My answer addresses this.
    – Allan
    Commented Oct 23, 2020 at 20:40
  • Thanks @Allan. I must note that changing the hardware did actually fix the problem.
    – Bunny Rabbit
    Commented Nov 4, 2020 at 5:04

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