External monitor problem iMac 2017 High Sierra.

Also having a problem after updating to High Sierra. I have one display connected with displayport and a second display connected with HDMI. I cannot get them to work at the same time. The mouse cursor is displayed on both, but one of the displays is always completely black. Which one works seems to be random and changes when I unplug one of them and then plug it back

This problem started for me last spring, when I was still running el capitan. My computer never had an issue connecting to two external display monitors, one through a mini displayport to vga adapter and the other from a usb to vga adapter, until one day the usb/vga-connected monitor stopped being recognized. I took the adapter home to test on my old monitor there, and it worked fine. I brought it back to work and tested it with a couple of colleagues' monitors, and it wouldn't work. I couldn't figure out why the adapter wouldn't connect to work monitors, so I ordered a different adapter. The new adapter didn't work, either, and the problem wasn't fixed when I updated to Sierra.

The info I received from Apple Support may be relevant (although not helpful) to those who have posted here:

"The MacBook Air supports up to one external display:

MacBook Air (13-inch, Mid 2013) - Technical Specifications

"The MacBook Pro models can support multiple external displays:

https://support.apple.com/kb/sp690?locale=en_US

So according to Apple, dual-external monitor displays will only work with MacBook Pros and not MacBook Airs. That's the dead end I've reached, which may or may not be useful info to others.

Hey everyone,

I had the same issue, after upgrading to High Sierra my external monitors would only show the mouse and otherwise just be black. I use a wavlink usb3.0 docking station to hook up my monitors and external keyboard and everything. After spending a stupid amount of time looking through this and other forums and not being able to reset the SMC, I realized there was a really easy solution. UPDATE YOUR DISPLAY DRIVERS AFTER YOU'VE UPDATED TO HIGH SIERRA.

if you use a DisplayLink system: http://www.displaylink.com/downloads/file?id=1033

otherwise try downloading the newest driver for whatever external display you are using.

Hope this helps, otherwise, good luck!

Hi RashDK,

You should be able to resolve the issue by just updating your DisplayLink driver. All external video adaptors (usb2hdmi/usb2vga/etc..) share the same driver.

They have an updated driver for High Sierra which fixed the same issue I had as the others in this thread.

Display Link Driver: http://www.displaylink.com/downloads/macos

Hope this helps. 🙂

I solved it, I have a MacBook Pro mid 2012, connect it with 2 Cinema Displays, one Display is connect it to mini DVI and the other Display is connect it by an adapter USB to DVI part # USB2DVIPRO2 www.startech.com, when I made the upgrade to High Sierra, this stop detecting the Display connect it via USB, after checking with Startech, I uninstall the driver from www.displaylink.com, first you have to disconnect your displays or monitors, uninstall the old driver, restart, install the new driver, restart and then, here is the point, Apple made some security issue in the High Sierra, you have to go to System Preferences, then to Security & Privacy (unlock) and in General you will see a message that a driver from displaylink needs your permission to work, then you allow it, and connect your displays and monitors and voila, it's working! works for me, hope that you can solve it too.

Reset the iMac's SMC and NVRAM

Reset the System Management Controller (SMC) on your Mac - Apple Support

How to reset NVRAM on your Mac - Apple Support

Try a different USB-C to DVI adapter.

Google Search: USB-C to DVI adapters

Just wanted to add that I sometimes have to use the following sequence to get this to work:

• Plug the adapter into the computer
• Plug the monitor into the adapter

If I don't, it doesn't recognize the monitors. It's likely that the monitors have to be "awake" to be seen.

I just fixed my issue finally.

I am using a MacBook Air

My symptoms:

The extended screen will go gray but i can still see the mouse.

In General, the extended monitor needs a third party program for it to work on the MacBook Air. it's called Displaylink

Everything was fine till the upgrade to High Sierra

My extended screen spec:

AOC e1659Fwu 15.6" USB 3.0 Powered Portable monitor w/ case.

• 1366 x 768 8ms (GTG)
• 500:1
• USB 3.0
• VESA Mountable 75 x 75 mm

Solutionnnnnnnn:

Reinstalling High Sierra didn't work.

- i removed Displaylink, ( uninstalled the third party old version, installed the latest version ) looks like i was using an older version of Display-link and I installed the newest version for Display-link and that worked yayyyy😁 I have the link listed below:

http://www.displaylink.com/downloads/file?id=1085

Sooo I am assuming whatever portable extended screen you're using, does it use a third party software??? if it does, go ahead and use the latest version and that might fix it instead of reverting back to an Older OS.

Thanks.

Youssef

Sure - here's the one I purchased. I ordered it on Saturday and arrived on Monday. RatsSmart Mini Displayport to HDMI 6 FT Thunderbolt to HDMI Adapter, it was $6.99 new on Ebay. I like how this one single cord as opposed to having a adapter connected to your HDMI cable. Again though my Apple adapter I have been using for 6-7 years so it was time.

Mini Displayport to HDMI 6 FT Thunderbolt to HDMI Adapter for Apple Macbook | eBay

ALSO - my bad my MBP 2011 has a Thunderbolt port not a DVI port that was a mistake on my earlier post.

I would also make sure you have checked all the suggestions in this post before ordering a new cable, especially resetting the system management controller.

1. Shut down the Mac and connect it to your MagSafe adapter and a wall outlet as usual.
2. Hold down the Shift+Control+Option+Power button at the same time for a few seconds.
3. Release all keys at the same time, then boot the Mac as usual.

Good luck,

JB

Hi,

I ran two monitors (and also used my MacBook Air's screen as a third display) through a thunderbolt dock, one using a thunderbolt to DVI adaptor the other a USB to DVI adaptor on Sierra, now with the upgrade only the thunderbolt to DVI monitor works. I have tried changing the monitor, the cables, swapped over to a HDMI to DVI cable which made the HDMI monitor work but stopped the thunderbolt one from working, even changed the dock to a Belkin one (which also used to work in dual screen mode). Found an article about how to roll back to Sierra, but this failed so I'm now using a complete clean install of High Sierra, but stuck with a redundant monitor and it's affecting my productivity.

The fact that Apple say it is not supported is neither here nor there, the fact is we were all able to do this and now the ability has been taken away. In my case I was not using the dual monitors direct but through a thunderbolt dock with a USB adapter for one of the displays and it worked rock-solid until this update.

I also have plenty of other issues including an HP printer that the MacBook Air now thinks is an unreadable external disk.

I would love Apple to be able to just issue me with a copy of Sierra that I can reinstall..............

I have same issue with a macpro (desktop) and sony monitor. I need to unplug monitor and replug to get the computer to work, and oddly computer seems to go to sleep after a while. BOth display and computer are set to stay on. Even turning off the tv and turning back on doesnt help; actually have to unplug and let it reboot

I am having a similar problem. I’ve submitted feedback to Apple about it. I have a 2016 MacBook Pro Touch Bar. Was very happily using a Thunderbolt 3 Dock with an external monitor until upgrading to High Sierra. The display is made by Dell. It has VGA and HDMI ports. I was using the VGA port with an Apple Mini DisplayPort to VGA adapter and it was working just fine. After the first High Sierra upgrade, the first problem was resolution. It was all stretched out on the Dell display. So, I switched to HDMI and use an HDMI to USB C converter. Then the supplemental update to High Sierra came out, so I updated and tried the VGA connection again. This time it was working and I thought the supplemental fixed it and I was relieved, but then my Mac went to sleep. I woke it up and the retina display came back on, but no response whatsoever from the Dell display. The only way to get it to come back on was to disconnect and reconnect the Mini DisplayPort connector again. Something is definitely broken when it comes to VGA connectivity and macOS High Sierra. I switched back to using HDMI again and it wakes from sleep just fine. It wouldn’t be an issue except that I really want to be able to utilize the Mini DisplayPort and have there other USB C ports free on my MacBook Pro for plugging in hard drives and other devices. It just doesn’t make sense why this would break in an update to an upgrade.