External monitor problem iMac 2017 High Sierra.

Today I have updated to macOS 10.13.2 and my curved Samsung external monitor is back to work!!! Thanks Apple.

But...

When I login to my MBP2017 from lock screen... I have a blue screen coming every 3 secs.

So half way, just half way to fix this external monitor issues completely.

FYI: when I plug the Satechi 4K hdmi dock from the type-C port and I plug it back in, the monitor works again.

Waiting for the MacOS High Sierra 10.13.3 update coming soon.

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.

I downloaded a new version of DisplayLink and my problem was resolved.

Getting a HDMI to thunderbolt adapter solved the issue for me.

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

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...

I had a chat with Apple last evening up to a senior advisor. Officially, they are not aware of any problem.... Besides, they don't look or trust the Apple Community discussions, which I asked them to. Finally, I hope I managed to make them understand that there are quite a lot of professionals and loyal customers out there who are getting upset because of not being able to do their job. They won't acknowledge that High Sierra s...cks for display connections, but I hope that the message will reach their brain.

However, they suggested to reset the VRAM, which could be a good idea (for those who don't remember, you restart while hitting alt-ctrl-P-R, and the system must do a "bong" sound, before you can release it. That will empty your video ram. I haven't tried yet (today my second display works... for now), but I wish I could try it and get some feedback from you guys, if you can try and see if it can help (at least until they fix the problem).

Resetting the VRAM did the trick for me too. I got my two monitors back. Now I’m noticing the fan going on nonstop when the two monitors are attached. It stops when I unplug them and use the laptop screen but, hey, it’s better than nothing.

So I sat at the Apple store for 3 hours with 4 “geniuses” working on the issue, and I think I may have solved. The adapters that Apple sells no longer output information from MacBookPro to display after an update, so the solution is possibly buying an independent USB-c to mini port display adapter via amazon. I found one for $19. It should arrive today and I will know if this works.

I got me a docking station (Caldigit USB-C Dock) to replace the Apple multiport Thunderbolt adapter and the external Dell display didn't turn black since. So it doesn't seem to have the problem.

SMC reset fixed it for me: How to reset the System Management Controller (SMC) on your Mac - Apple Support

Read the thread above. Lots of people are having luck installing the DisplayLink driver mentioned in several posts.

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.

so i have two ASUS monitors, and mid-2012 MacBook in the middle - left monitor is OWC usb to dvi adapter. right is thunderbolt to HDMI... Sierra, all worked great. then after updating to High Sierra, i'm with the same drama as those here. only the laptop and one monitor would work. or if both connected, the left and right would work but laptop would not. reached out to the guys at OWC where i purchased the usb to dvi to HDMI adapter and advised to update the drivers for the usb adapter, then do the 'resets' after a shutdown...still didnt work fully both the externals would show but the laptop would not.

it was suggested i drop resolution on the laptop itself, (but monitors are still the same). so my laptop now is 1280x800, and the two monitors are still 1080p as they were pre-upgrade.

so i'm at least back to where i was before, but not 100%.

Maybe this helps someone else, until apple fixes the real problem - have a great day!

Having the same issue here. Triple monitor setup that worked for years suddenly stopped working with this update - proof of working solution @ https://mkn.us/blog/how-to-use-3-external-monitors-on-macbook-pro-2015/

The mentioned solution utilized standard active cables rather any additional USB / software / drivers.