MacOS Sierra not recognizing external displays and going black

I checked the Nvidia website for mac drivers for sierra. LOW AND BEHOLD! THEY EXIST!

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.

Didn't feel the need to search for drivers until I installed MAC OS SIERRA.

EVEN THOUGH I LOVE APPLE! GREAT PRODUCTS! SHAME ON APPLE FOR GIMPING THE GRAPHICS DRIVER IN AN ATTEMPT TO FORCE UPGRADE!!

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!

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.

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.

MacBook Pro (Retina, Mid 2012) - Sierra - 10.12.3 - Having same problem. Blank retina display on restart. Cannot safe boot or recovery boot. But, can login using teamviewer and can recover via sleep and wake tactics. No clear pattern. No external monitors are detecting. But, when removing connection to monitor (HDMI or Thunderbolt), the LCD screen resets. Still trying to identify patterns that cause this.

I get no console notification when plugging in monitor. But, when I disconnect monitor (HDMI or Thunderbolt), I get the following:

[ERROR] - Driver reported mode info is out of sync with current mode info. Display 42803c0, driver's bytePerRow = 11776, driver's width = 3360, stored width = 3360. Forcing rowbytes to be 4*modeInfo->ioModeInfo.nominalwitdh.

Biggest concern is lack of visible Apple at startup - and no ability to get into recovery mode. These are critical problems I can't address. I have reset VPRAM and other suggested procedures. Nothing has worked.

Just wanted to give you guys an update. It seems to be fine after I updated my Macbook Pro to the latest Mac OS Sirrea 10.12.2. No more black screen at start up or reboot.

Macbook Pro 15 (Mid 2014 with NVIDIA GeForce GT 750M)

Samsung 4k (U28D590) Display

Mini/thunderbolt display port cable.

I recently had my hard drive replaced (for a recall), I was on Sierra before and my external display had no issues. After I got my hard drive replacement I am experiencing the same issue. This is 100% software related, nothing to do with age of the display either. I've searched several different forums for an answer and spent far longer than I should have. I've really enjoyed Apple's operating systems over the last several years but this is probably my last straw with them. Known issue for several months and no feedback anywhere from Apple. For some people being limited to only one display greatly limits productivity.

I have the same issue and I have updated to Version 10.12.2. I'll have to try the DisplayLink driver (3.0 beta 2 - 23 Dec 2016) but so far what worked was unplugging my adapter for my external monitor AND also my ethernet to USB adapter and the Mac will start showing the Apple logo with the progress bar. (Don't need to force shut down and press power again).

Had a user with this same issue. Seems an aftermarket dongle will not work. You have to go out and buy the OEM Mini DVI adapter made by Apple specifically for it to work. Is this a software issue I doubt it. It seems that Apple made it this way by maybe embedding something in there dongle that only works for there laptop. When going from the Mini to the dongle using a digital signal and then to an analog signal such as VGA this is when the case is present. Not sure it this issue is present when going digital to digital. Regardless, did Apple force people to buy there product and not allow for the use of aftermarket content. Also, tried it with aftermarket dongle that is manufactured after sierra came out and it does not work. Tricky or Shady? Which one?

So here's my issue. I had an aftermarket Monoprice MiniDisplay to VGA dongle that worked fine with my Mid-2012 MacBook Pro 15" on OSX, El Capitan, and Yosemite and an NEC projector. I then downloaded Sierra 10.12.1 and the dongle no longer worked! Tried with a different, newer aftermarket MiniDisplay to VGA and still nothing. My MacBook Pro 13" running El Capitan was able to connect with the new, but not the old Monoprice. The only way I could get either dongle to connect with the MacBook running Sierra was if I shut the computer down, connected to the projector, and booted the machine. The dongle would then allow the laptop to connect to the projector. Once I disconnected the dongle while the computer was on and tried to reconnect, it would no longer detect the projector. I sometimes use this dongle to connect to my 60" Vizio SmartTV via the VGA port on the TV. It sends the signal fine and I am able to connect, even though I have Sierra installed. Went through all the steps listed in this forum. Reset the NVRAM, reset the PRAM, reset the SMC, went through all the garbage in the "Display" tab in System Preferences, clicked Option while in Displays and selected Detect Displays, updated to Sierra 10.12.2, downloaded and installed DisplayLink Driver, tried to run Mini DP VGA Update (did not recognize any display to update), booted machine in Recovery mode and did a Re-Install of Sierra 10.12.2. Finally, I bit the bullet and spent the $30 on an Apple brand MiniDisplay to VGA adapter and, drumroll please.... It worked! So what have we learned here? There has to be something in Sierra that is recognizing I am not using an "Apple approved" or "Apple brand" adapter. The Monoprice is passive and not bi-directional, not sure about the other aftermarket one I have. But both worked on earlier OS's. I know the Apple MiniDisplay to VGA is active, is it also bi-directional? Is this perhaps the reason it works? Since it is bi-directional, it is allowing the projector to communicate back to the laptop? It will be interesting to see how all this plays out. I am hanging on to the aftermarket adapters and will try them after future updates. I know Sierra 10.12.3 beta is out for Developers, so we'll see what comes next.

I'm using club3d DVI-HDMI adapter with my Sony X800D TV. The adapter was working just fine with El Capitan. I just updated to Sierra (What a bad decision) and now it stopped working. All I can see is black screen with pink bar at the top on my TV. Club3D is also passive, so I'm not sure why Sierra doesn't like it. What a bummer.

I have the same problem now. I've been using a MacBook Air (Mid 2013 Haswell model) connected to a 34" Ultra-wide monitor at 3440x1440 resolution. I know this MacBook air can't run this res at 60hz, so I've been running at 30hz until I can upgrade my laptop. It worked fine until I installed 10.12.3 this morning, and now nothing! I connect in using Belkin mini-dp to dp cable. When I connect in the display, the MacBook display blinks for a second, then stays on and the display never connects. I noticed the release notes say it "improves MacBook Pro graphics switching." Well I'm wondering if that's screwed me up though!

I don't think it has to do with monitor. I have Macbook Pro 15" (2015) and using Club3d DVI-HDMI adapter to output 4k@60Hz to my Sony X800D TV. It's fairly new model (Sony released it last year) and working just fine with El Capitan. This morning, I updated to Sierra and the adapter couldn't output 4k@60Hz anymore. My TV just shows black screen with pink line at the top. So many people are having the same issue with external TV and I have no idea how to fix this issue. Now, i'm trying to remove Sierra and reinstall El Captian.

After upgrading, my external display only works if I unplug it before booting up. After the desktop appears, I plug it back in and it works properly. This is quite annoying since my MacBook display is shattered and I cannot see the sign-on screen. I finally figured out that I could blindly type the first letter of my User Name, followed by the return key, followed by my password to login.

I figured something out for this issue. I've been using a Henge Dock for my Macbook Air so I have to close the lid and connect it to power to dock it (and the external display doesn't work under Siera). The other day I tried hooking up the display while the MacBook was open and running and it worked! I could subsequently close the lid and the external display still worked. So for some reason, Siera won't let me hook up an external display with the MacBook lid closed. FYI APPLE - Fix it please!