External monitor problem iMac 2017 High Sierra.

I have the same problem with my Mac Pro 2013 and two Apple Thunderbolt Displays. Worked fine in Sierra but not in High Sierra! When the screens go to sleep I can't get them to work. I must hard reset the whole system to get them back. Not good at all.

Apple has made it where you cannot do anything that has the Apple brand on it. Lazy and arragorate development could be a case! For example, I had the ability to use the USB mac to connect to any monitor (usb or thier connector). Why and should an update make things not work in the past such as connecting to a **** monitor? Should thier development encompass and include things you use and the newer things to use on your mac? They spend on marketing and branding to sell us slight improvements because you belong to the Apple club! Typically Apple will believe it's being this single proprietary hardware and software is the "all. " Case and fact and google it. This High Sirrea update has cause so many issues with everyone out of the blue... WHY! Thanks again Apple!! People don't fall for this. Seek everything and anything that leads you not depending on this arrogance and the power of stock holders that it's aim to make you have the best and current greatest.The PC is comming back as more flexible and more powerfull!

Also having a problem after updating to High Sierra. I have one display connected with display port 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. I tried twice rebooting the MacBook Pro, no change. I am at stuck with one monitor at work, that hurts. Display preferences shows both monitors with display names, so I am not sure why one (DELL P2412H) is black screen.

Bought my Microsoft Surface Pro 4 today, because I could not handle not using both my screens anymore. Best part is you can eliminate 2 devices with it( MacBook Pro & iPad Pro), going to be interesting going back to windows after +/- 10 years on OSX. Will keep everyone updated on my progress. Although I think I should be OK, as most of my day to day is MS Office (with OneDrive) and Adobe Creative Cloud. Got Spotify Music too. Easier than ever to change across. Will be keeping my iPhone, but will be monitoring other alternatives.

I am having the same issues with my external displays. I just switch to MACBook Pro after 2 years of hassles with Windows 10 products and High Sierra is just like that experience. Very disappointing for my first Apple experience.

Good for you but still not working on my MBP 15’ 2017...

Tried everything, even buying a different usb-c hdmi adapter other than satechi like belkin (sold in all Apple global stores therefore fully compatible with all Apple products) and still having mouse cursor freeze for 2 secs every 2 secs of movement on both screens (laptop and external Samsung 34’ curved monitor).

This means that the problem is in the High Sierra OS...

Desperately need to work with my external monitor!!!

Reality is: Apple stuffed this up, so Apple must fix this global problem ASAP with an update.

Back to work Apple and just do it

Still the fact that Apple didn’t go through all testing with High Sierra before it public release (mistake or...) and now we (customers) after we paid lots of money for our Apple computer and a an external monitors, now working too hard every day with reduced performance because of the external monitor not working anymore and even try to make it to work ourselves spending more money and time on posts and troubleshooting !!!

Are we crazy?

Apple is responsible for this and the whole world know.

They have to put the good part of the code of Sierra, where all external monitors were working and past it into High Sierra. It’s not hard for them come on!

No. I may revert it back to Sierra but that will require 60 to 80 hours to get it all configured and everything installed again. I also might play with it as a headless Mac Mini if I can convince it to come up in a reasonable resolution with an EDID plug. The advantage there is that I can test it with each minor High Sierra update. I don‘t see myself ever buying another Apple device which does not come with an integrated screen. Although the Mac Mini is a perfect device for KVM use I can’t go through this every year.

I bought a new MacBook Pro yesterday. My apple Thunderbolt Display works going from my computer's USB-C port through an apple adapter into the Thunderbolt Display. My Samsung
TV does not work going from my computer's USB-C port through an apple adapter through a Thunderbolt(original)/ HDMI cable into the TV. I upgraded my DisplayLink software, but that didn't solve the problem, although somewhere in the process it implied that the DisplayLink software was USB related, not Thunderbolt related.

Well just got the latest High Sierra... Mac mini still does not automatically sense or retain resolution with HDMI . Still need to do the 90 degree rotation and revert procedure to get it to detect it. If I don’t I cannot see the top menus or the bottom dock, pretty much making my Mini unusable.

Ok, I made the stupid mistake of allowing my newer Mac Mini to get minor updates... security updates to Sierra. It no longer detects my monitor . I am going to buy a Dell as I need a working machine

i have a very similar problem. my external HP ZR2440w with an hdmi to hdmi cable works fine - even after the update to high sierra. however, i have a separate external monitor, an HP Z24i, with an hdmi to display port connector that i use at a different location where i travel. the mac cannot detect that monitor.

does this mean that high sierra can't support an hdmi to dispay port cable?

I tried USB-C -> Displayport and it doesn't work for me :-( (I have a Dell U2717D)

I am starting to be desperate about this. Thinking about selling my monitor and buying a new one. I don't understand how Apple can do this...

I feel for you but Cnet has highlighted a potential problem with this monitor when connecting to USB-C

Dell UltraSharp 27 (U2717D) review - CNET Not fair that Apple effectively makes people's hardware obsolete in this way though.

I thought I'd solved all this after the upgrade, by updating the DisplayLink software. All of a sudden, with the update 10.13.2 am back to square one, 2 screens, except that now not even Finder or the Dock are jumping across between the screens as they normally do, so in effect, 1 screen! I have a Samsung 2243BW, bought especially to increase from 3 to 4 monitors for my home studio. Bought an Apple dvi adapter, and nada. I now cannot even get the PGA connected other monitor that previously worked fine to function at all. I cannot run Logic Pro in full screen mode because it blacks out the other screen, so I'm effectively having to stop a session, and minimise Logic in order to pull up a synth or effect - anything really. No other way I can do it. I can't really see the mixer properly in bigger orchestral scores, because I cannot use full screen mode on either screen. Am a new startup, this is adversely affecting my work, and I do not understand where the problem stems from and why it hasn't been sorted by now? Displays worked fine with "Low Sierra," so how can Apple have become so inept as to have created a problem, and a serious one, with this Godforsaken upgrade..!