External monitor problem iMac 2017 High Sierra.

Jesper/ All,

I to was having a similar issue running dual monitors after upgrading to high Sierra, my newer monitor would work however not my older dell monitor. I finally went and purchased a new monitor made by AOC pretty cheap, bought a HDMI to lightening port adaptor since my first monitor was using the HDMI port. Surprise after rebooting my Mac Book Pro all screens came up and no issue since. I hope this helps!

I am running a MBP with 2 external monitors, 1monitor via HDMI cable and the other via MDP-DP cable, after upgrading to High Sierra, it won't recognize the MDP-DP monitor, however the HDMI works fine.

Also when I try to connect the MDP-DP monitor, my MBP reboots.

Believe it is a Apple problem, and would like it resolved ASAP.

+1 - I have three external monitors connected to my 2015 macbook pro, and keep the computer itself closed and in a Henge Dock. The monitors are connected to the two mini display ports and the one HDMI port. Since the macbooks internal graphics can only support rendering two monitors, I use an active adapter to make the third monitor possible.

This worked perfectly before High Sierra. Now only two work.

Wait before celebrating. Here's what I've observed.

First I fully restarted my iMac 27 (2013), then plugged an ASUS HDMI 27 via a HDMI to mini display connection.

for like an hour, High resolution, stable, no problem. Then, the ASUS starts to turn dark for one sec, then 2... and after 2 hours, got totally crazy (dark, low resolution) and fully unstable. I have also some random issues with my iMac display when on Google. So, based on what I've read and observed for myself, I have the feeling that the High Sierra OS has flaws regarding the video control, which will solved once Apple decides to tell us what is going on...

So far since it has been a week without a single issue using the HDMI to lightening port adaptor I bought it for $24 dollars at Best Buy and has been stable. I won't pretend this will resolve everyones issue but in my situation it did I also feel that the new LED monitor does help I would have tested it with an older dell 21" but they didn't have HDMI support.

My Samsung U28E510 is still recognized but is out of whack. The mouse cursor is in a different position than the system thinks it is as if the resolution scaling is messed up... The cursor only shows up in a box that takes up about 80% of the screen, and won't go past that. If I close the lid on my MB Pro and then figure out how to correct for the messed up positioning of the mouse, if I then manage to click on a scaled resolution change, it works, but if I open the lid, things get out whack again.

I'm having similar issues. For me, it's a blue screen from on my external Samsung U28E590 via a i5Create multi USB-C adapter. My workaround is that I installed SwitchResX and when the external monitor is connected, use the software to force a minor change, like frequency (30 Hz to 60 Hz, to 60 to 30 Hz), under my target resolution. I need to do this each time I plug in and try to use the monitor. I bounce my MacBook Pro back and forth from a work setup to a home setup.

High Sierra 10.13.1

2017 15" Macbook Pro

3.1 GHz i7

16 GB memory

I tried running that, and it said my disk didn't meet the minimum requirements. Of course it doesn't tell you what those are and why my drive was good enough for High Sierra but not this update? Come on.

Posting here incase this helps anyone else:

I too upgraded to High sierra today and then my internet and my dual screens didn't work anymore. Internet was a quick fix, but dual external monitors was not. I finally got it fixed when I reinstalled a driver for the dual monitors that I am using, mine happens to be Display Link.

Same problem after update MacBook Pro 2017 to macOS High sierra and connect Samsung 27” 4K curved the mouse freeze for 3 secs and moves only for 1 sec.... basically impossible to do anything on the computer!!! Frustrating! How it’s possible to spend $5000 for a laptop and after an os update be unable to work! I’m losing money and time at work because of this...

The question is: who’s going to pay?

Is Apple checking and testing the updates before they are getting released? I don’t think so but is time for Apple to release a patch for this issue in no time before the entire globe goes crazy!

Please fix it ASAP

Unfortunately, not from my (our) knowledge. Let's hope that they will come with an update soon... As usual, Apple doesn't communicate about their failures. I learned my lesson: next time they come with a major upgrade, I will wait for a couple of months and check the users' discussion posts before doing it.

My personal experience with an ASUS 27 connected (HDMI to mini display) to an iMac 27: totally random and fluctuating issues. Can work well for 2 hours, then, begins to turn black for a while, or even doesn't switch on (even if detected in the preferences). From all posts, whatever the display and way to connect it, it appears that there's a flaw in video monitoring from the High Sierra OS, and it has to be fixed by Apple. It's quite upsetting to see that they don't communicate on it while, in the same time, they claim they provide the highest service to professional and graphism, photo, and media... "So Sad!" as a US President could say....😉

Have had this problem since I jumped fra Mac Air thunderport to HDMI to new macbook with USB-C hub ( 1 usb, usb-c and hdmi)

I can restart with no connector, and then plug it in after startup, and mostly be good.

If it starts cracking up, I just pull my powerplug and it it 100% stable. But then im on battery for a limited time...

So it IS a power management problem...

Thanks for the DisplayLink driver. At my workplace, we use wavlink, but did not see any updated drivers for macs. I installed the driver above and was able to have dual displays (MAC laptop and Dell monitor), but was unable to use the mirror feature on the mac or it would log the user out and reset to dual display. Hope this helps!

http://www.displaylink.com/downloads/file?id=1033

I have three external monitors attached to my MacBook Pro. I upgraded to High Sierra this morning and now two of them don't work. I need to go back to Sierra because I need my three monitors. How do I do that?