MacOS Sierra not recognizing external displays and going black

I had the same issue when updating to OS High Sierra. Are you using an "Other than Apple" adapter to connect the monitor to the computer? I am using a j5create usb 3.0 to vga adapter and went to the j5create website and downloaded the software again for this specific adapter. My external monitor immediately worked again after restarting.

This issue is due to the motherboard of the retina mid-2012. Unfortunately nothing can be done except one thing, call apple and try to use the extension program for video issues:

MacBook Pro Repair Extension Program for Video Issues - Apple Support

Note that this program covers affected MacBook Pro models until December 31, 2016 or four years from its original date of sale, whichever provides longer coverage for you. The following models are no longer eligible for this program: MacBook Pro (15-inch, Early 2011), MacBook Pro (15-inch, Late 2011), MacBook Pro (17-inch, Early 2011) and MacBook Pro (17-inch, Late 2011).

At this date (i.e. 01-dec-2017) it means that only retina mid 2012 bought in December 2013 on the refurb for instance are still elligible to the repair extension program. If you are not elligible call apple anyway and try, who tries nothing has nothing.

I might have found a temporary work around from this site and quoted below: https://www.displaylink.org/forum/showthread.php?t=65562&highlight=high+sierra

Yes the mirror issue is still there. The only way to mirror currently is having a Mac with discrete graphics and making sure the discrete graphics is active (opening Photos for example).

We have to continue pushing for this to be resolved by Apple.

I don't know what "discrete graphics" are, but I opened Photos as was suggested, and while my MacBook Pro screen still goes black, I am able to see it on the TV now.

I might have found a fix...at least a temporary work around. I found this on a DisplayLink forum:

Yes the mirror issue is still there. The only way to mirror currently is having a Mac with discrete graphics and making sure the discrete graphics is active (opening Photos for example).

We have to continue pushing for this to be resolved by Apple.

I don't know what discrete graphics are, but opening Photos before I plugged in my Targus 110 seemed to work for me. My MacBook screen goes black, but I can see it on my TV.

Had similar issue with MacPro 5,1 after updating to OS High Sierra. Hope you don't mind I piggy back off your post to help someone else with this headache. I've been diddling around with trying to make the second monitor display work for several days.

Have an old 5,1 tower, but its new to me. Upgraded the Graphics Card from Radeon HD 5770 to non-mac EVGA Geforce GTX 980 Ti. This 980 card worked just fine with dual displays in the other tower, a 4,1 version, but with the new OS I lost the ability to see dual display.
-So took out the GTX and put the Radeon back in.

-Wiped the SSD drive and reinstalled an older OS Sierra back to 10.12.6 (for 16G29 version) from Apple here: How to download macOS High Sierra - Apple Support
-After the long, painful OS reinstall, reinstalled the CUDA and Nvidia drivers.

1) Nvidia QUADRO & GEFORCE MACOS DRIVER RELEASE:
(version 378.05.05.25F01) found @ http://www.nvidia.com/download/driverResults.aspx/120845/en-us

2) Nvidia CUDA 8.0 For Mac OS X Release:
(version 8.0.46) @ http://www.nvidia.com/object/macosx-cuda-8.0.46-driver.html
-Restarted again.

-Went into System Preferences and selected CUDA Preferences, updated the available driver via the 'Install CUDA Update' button.

-Restarted

-Still got single monitor display.

-Along the way I'm sure I read here to download DisplayLink, not convinced it solved the issue since I still only had one monitor display activated.

-Found happy accident by switching around the DVI connectors between the ports on the back. One monitor was straight DVI because of the native ports available on the GTX 980 (1x DVI, 1x HDMI and 3x Display Ports), which always worked. BUT the second monitor's DVI was adapted using a DisplayPort to DVI plug. After fiddling the cables around like a game of musical ports, turns out the DisplayPort adaptor wasn't seated properly and caused the flimsy loss of connection.

Was this worth several days of reinstalling several versions of macOS to revive the second display? You betcha!

Thanks for sharing this! I have a Late-2012 iMac. My 2nd external monitor went black quite a while back (even tho it showed in the monitor "arrangements" window. This fix brought it to life again! Much appreciated.

TmacKilla's link and Instructions:

http://www.nvidia.com/object/macosx-cuda-8.0.46-driver.html

This little driver made my 2012 Mac Pro Retina with 660 GTX actually fly and run way more efficient graphic wise and fixed my external monitor hiccups.

you can update via system prefs.

I had the same problem but was able to fix it by reinstalling the latest update to DisplayLink that is more compatible with the new IOS. Hope this helps.

http://www.displaylink.com/downloads/macos

HDMI to my LG TV failed after High Sierra upgrade.

Installed that DisplayLink driver above. Bingo! All sorted.

Cheers tiffyzsmile 🙂

thank you, thank you!! Had two Cinema display's - on iMac with High Sierra. Left Display would not work whatever I did. After installing Display Link - it worked! No idea why - but very happy!

Just bought a new MacBook Pro 15'' Retina, OS Sierra V. 10.12.

Tried a bunch of online solutions to make my Samsung external monitor to work and nothing solved.

I'm using a HDMI/Thunderbolt Cable into an apple adapter to Thunderbolt/USB-C.

gianberselli wrote:

Just bought a new MacBook Pro 15'' Retina, OS Sierra V. 10.12.

Tried a bunch of online solutions to make my Samsung external monitor to work and nothing solved.

I'm using a HDMI/Thunderbolt Cable into an apple adapter to Thunderbolt/USB-C.

I believe you may be using the wrong mixture of cables.

Please clarify: are you using a Thunderbolt 3-to-Thunderbolt 2 adapter, and then a cable with Thunderbolt connector on one end and HDMI at the other? Or is it a miniDP-HDMI cable? miniDP has the same plugs as TB2, but they're not the same thing; the TB3-TB2 adapter does NOT carry the miniDP signal.

You should be using a USB C-HDMI cable or adapter, or a USB C dock with HDMI.

Hi. I've been using a LG proyector (AN 110B) with my Mac mini for years through an HDMI connection. Now stopped working. I can connect the Mac to another proyector and the proyector is working with other devices, but when I put them together, "No signal" message appear... I'm struggling with it within the last days... chating with LG and Apple service without any result... they blame the other... I can use the thunderbolt-HDMI to work with the Mac mini in my SONY TV, so I can try things... nothing is working so far...

I'm desperate...

Any help?

I have the same issue on my late 2013 Macbook Pro with MacOs High Sierra. Neither my HDMI port works nor my external display through thunderbolt. My old 27" thunderbolt Mac Screen does though. This bad... :-/

HI,

I have MacBook Pro Retina Retina Mid 2012 (High Sierra 10.13) and I have problem connecting it to my SONY projector via a HDMI cable. I tried SMC reset but it is not working. The screen will just not detect any output. I tried it with my SAMSUNG TV with a different HDMI cable and it still doesn't work. Anyone having the same problem or found a solution?

Nope. I tried that, restarting my mac. The sound works through the hdmi cable, so I am sure there is nothing wrong with the projector and cable. The projector just stay on the default blue screen, don't even have the option to select a hdmi option. Has anyone try downgrading back to El Capitan?