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I have a MacBook Pro (Retina, 13-inch, Early 2015, macOS High Sierra 10.13.6) which fails to detect an external display after is has woken up from sleep. (Update: Now running macOS Mojave 10.14.5 on a 13-inch 2018 model, and this is still a very annoying issue).

Here's my situation: I have an external monitor hooked up to to the MacBook's display port, I walk away from my computer for a few minutes and it goes to sleep. I come back, and no matter what I try, the only way for the MacBook to detect the external display again is to restart the computer!

I'm using a Mini DisplayPort to DisplayPort cable. I use the MacBook at home as well as at work; I've tried different ports on my computer, different cables, and different monitors; the issue is with the MacBook itself.

It used to be that when this happens, I manually put the MacBook to sleep and wake it up again, and voila, it would detect the external display again. But now the only way to consistently fix the issue is to restart the MacBook.

I've also tried opening the display settings, holding down the alt key, and clicking "Detect Displays". This does nothing.

Any ideas on how to remedy this problem?

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  • Exactly same symptoms (MBP 2017). Only reboot helps. Tried to replace all cables, and tried 2 different thunderbolt docking stations. SMC and PRAM resets did not help either.
    – Dmitry
    Oct 26 '18 at 17:48
  • 18
    You'd think a trillion dollar company would put up some money to iron this bug that's been around for so long. Apr 10 '19 at 4:51
  • 11
    Still an issue on the newer macs :'( May 18 '19 at 14:30
  • 4
    Since there's apparently no solution to this except rebooting or plugging cables around, I suggest that everyone that has this problem creates a bug report at Apple, otherwise they might not notice. I have submitted a bug report including a video of the 2 displays flickering today.
    – narrowtux
    Jan 22 '20 at 14:00
  • 1
    February 2021 and having the same issue with my brand new macbook pro. We should definitely fill bug report.
    – The Doctor
    Feb 3 '21 at 21:54
6

I still have the same issue on a macbook pro 15' 2018.

Unplugging and plugging again the screens helps without having to restart the whole thing... except that all open windows jump to the main screen.

.

///// EDIT solved the issue through an external thunderbolt dock

I am using the Thunderbolt 3 Dock of Glyph now. My external screen is connected to its Display Port port. After waking up the screens behave normally. When I take a break, I power off the external screen and power it on before waking up the computer. In the tips I got from Glyph, they do ask you to turn off Energy Saving options when connected to the dock, but it all seem to work fine,

4

I've found the system knows the other monitor is there, it just can't rouse it. Fastest work-around I've devised so far:

  1. Open System Preferences
  2. Go to 'Displays'
  3. Click 'Gather Windows'
  4. On the panel for the external display, choose one of the rotation options. (Seems that forces the system to give itself a kick and the external display will wake up, albeit upside down.)
  5. Helpfully, there's a 'Revert' button already focussed. Just press Enter on your keyboard and it'll spin back around.

Done.

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  • 2
    That doesn't work for me since it doesn't know the other displays are there, so not "Gather Windows" option.
    – Gabrie
    Aug 7 '20 at 13:27
  • Works for me, though rather than rotate, I moved the relative window position a tiny bit. Oct 13 '20 at 9:49
  • neither gather windows + rotate nor moving the arrangement works for my mbp 2016 13" on 10.14.6
    – rockhammer
    Nov 6 '20 at 18:37
1

I experience similar problem and Google brought me here. Though as long as I don't unplug the cable it would always work fine. If I unplug it to take away the laptop and come back again one of my two monitors (the one converted from Thunderbolt to HDMI) won't work. However the other one with Thunderbolt to DisplayPort always works.

My solution is to connect it to a different port and most of time it would just work again.

1
  • I've experimented with this, and the following seems to work: - Connect the monitor using a display port - Set on the monitor the display port version to 1.1, not 1.2 Hope it helps someone... Jun 1 '21 at 20:25
0

I FINALLY found a method that works every time -- it's half voodoo, half witch's brew.

my setup

I'm running a 2019 MB Pro, one monitor connected via dock and display port, one monitor connected via usb-c adapter and HDMI. In my case, the display port monitor was one that never would wake from sleep. After much fiddling around with trying different methods, I found a way to reliably start using both monitors again without restarting.

steps to get all external monitors working again without rebooting

  1. Power OFF the display port monitor
  2. Wake computer from sleep
  3. Wait until I see a stable display on the HDMI monitor
  4. Power ON the display port monitor -- flickering on all screens ensues as the computer attempts to wake the displayport monitor up
  5. Unplug the dock (the display port monitor) from the Macbook
  6. After a moment, plug the dock back in.

Don't know why this works. Until I figured this out, the only way I could get it working again was to restart the MB Pro.

Hope this helps!

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