External monitor problem iMac 2017 High Sierra.

Having a mac pro, there is no alternative except an external monitor.

Since the beginning if I unplug the monitor, then turn it back on, it works. Turning on and off on the remote doesnt do it.

I bought a smart plug so I can do this via Alexa, which isnt perfect but at least is easier. Wonder if anyone else finds that unplugging helps

Thanks for that Big64 - have downloaded that... Cant find it now, mind you, but I'm assuming its in there some where doing its thing!

I'm drifting slightly off-topic here, but it is monitor related: has anyone noticed that if you choose your own desktop image, when you reboot, it goes back to the 'default'... Normally - this would be no more than anecdotal, but it occurred to me that if the designers at Apple have begun exerting their own tastes over those of Apple customers, does that not suggest a divergence from the founding philosophy of Apple - that of the ability to express oneself, ok - within a framework identity that was distinct, ie that we bought into the "Apple brand, feel, palette" BUT... the big difference was that the computer served the - especially creative/artistic - human operator, not the other way round..? If I wanted the other way round, I'd have stayed with Microsoft!

This worked for myself as well. Note: I'm using the VanTech USB 3.0 To HDMI Adapter. It uses the display link driver, but the official download on vantech is v2.5.1 while the display link driver is v4+.

Ive got the same problem too - at least I now know its nothing I've done - thats Apple. Where is your Quality and Testing? Not amused.

I look forward to a High Sierra update asap. I, as MANY others now appear also, have a useless external screen. The curser moves across the screen, but it remains black and I can't drag any windows on to it. :-(

And HOORAY!! Checked the monitor (an old HD Ready TV, but did the job admirably), and it had breathed its last. Found another, less old TV last night on a local auction app here in London, and hey presto - this morning, connected and turned on - got an image immediately, and it's been good as gold all day!

I've got a 4th monitor (yep in a studio - even a home one - you need at least 4!) arriving at the end of the week. That'll be the largest numbers of screens I've ever run. I'll post how it goes. So, it might be something Apple just fixed, or the 'displaylink' software Big64 shared with us previously, or running Onyx (for High Sierra) sorted out some permission bottleneck, I cannot tell you. I'm not that 'au fait!' But it being something 'deliberate' by Apple, I think we can scratch that out. I do wish they'd leave us with the last say on desktop images, though. Much as I think that landscape is impressive, I'm trying to do photos for my new website, and want the website backdrop on all monitors. High Sierra keeps changing it back!

This is so much Bullsh*t, I too have the same issue, the mac does not recognize the external screen, what is Apple taking so much money for? I'm not recommending Macs to anyone if this persists. Apple needs to fix this soon.

Same problem here with brand new Air. I've got 2 external displays, one through thunderbolt which is working ok and one through j5create usb display adapter which is black, only mouse pointer visible.

Got this answer from j5create support:

Unfortunately, our USB display and Ethernet adapters, as well as our docking stations, are not currently compatible with the new Mac OS X High Sierra 10.13 operating system

....

The current ETA for the new driver software is later this week!

Hi Everyone,

Just to let you know that the latest upgrade for High Sierra that came out today has fixed the video problem for me, I now have both my external monitors working! I do hope that this update solves everyone else's problems as well. Just to let you know that the second monitor only kicked in after a full shut down and disconnecting and reconnecting the USB cable from my thunderbolt dock.

A big thanks to the Apple devs for sorting this out, I just hope it doesn't happen in future upgrades as I've felt like I'd lost an arm or something whilst the monitor wasn't working!

Got to add a BIG thanks and "GROUP HUG" to the whole Apple Family (that's QUITE a hug!!). I've got 3 monitors fine, 4th due here tomorrow - it'll be the most number of monitors I've ever used!!!

Now... can we PLEASE - APPLE - be allowed to choose our own Desktop images..? xxx

I have a new ASUS display plugged on my iMac 27' (2013), with an HDMI to mini Display port, and I have recurrent issues (in other words: display recognized but unstable or totally black). I tried with my MacPro, same connection: same problem. I tried directly via the HDMI port, and it works well.

So, I agree with you that there's probably some "issues" of connectivity with High Sierra...

I had previously used time machine to go back to working Sierra being unable to resolve the issue with High Sierra. After reading your post I had to try High Sierra 10.13.1. Unfortunately, I am unable to use either display when I have the Thunderbolt to HDMI adapter linking my external monitor. The display on iMac goes blank as well as nothing on my external. I will try a complete power down and the reconnection process now. Haven't tried my MacBook Pro with HDMI to external but I will and report back.

Well, the complete shut-down of iMac didn't work. I am able to use the HDMI out to extend my display normally using my MacBook Pro. I will be glad when this problem is resolved, but for now I think that I will have to go back to Sierra.. I really need the extended monitor for productivity. Good luck everyone, please post if someone thinks they may have found a complete solution for the Thunderbolt / USB-C connector. Just for the record my iMac is a 2013.

Thank you,

Jack

Apparently, the last update (10.13.1) worked for me. I have my 2nd display plug via the HDMI to minidisplay port, and it's stable. I just notice that when the screen saver switches to another photo, it takes 1-2 sec to adapt.

I addressed that issue to my computer technician and he made me buying a new connector able to support HD and 4K (StarTechcom MDP2HD4KSW). Apparently, the old Apple connector I had was not able to do the job. So, this could help as well.

Hope it helps

Best

Eric

I spoke too fast... The system went asleep and back. It doesn't manage to stabilize (turning black, showing low resolution...). Seems the problem hasn't be fixed yet. It was stable when I totally shutdowned and restarted my computer. I don't want to do it every time...😟

FYI, my display is connected via a brand new HDMI to mini Display connector

Last night I reloaded High Sierra with all of the latest updates and this appears to have fixed the issue for me. Having said that upon reboot I did have to unplug and reconnect my monitor to get it to work, but its been fine since, so perhaps this is the step that other will need to take to get things working. I have a 2017 iMac connected using a USB-C to HDMI lead if this helps anybody.