External monitor problem iMac 2017 High Sierra.

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. 🙂

For anyone with an older monitor that uses a DVI connection and needs Thunderbolt 3 (USB-C) to connect to a 2017 iMac – I spent several weeks researching, finally ordered what I thought was the perfect adapter, and it was a complete fail. The iMac didn't even recognize that another display was connected – zapping the NVRAM, resetting the SMC, nothing helped at all. Did some more research and found this cable, and it worked like magic the second I plugged it in!

https://www.amazon.com/gp/product/B0761LK6XF/ref=oh_aui_detailpage_o01_s00?ie=UT F8&psc=1

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

I have this issue and troubleshot mine down to some specific items. I have a 2017 15" MacBook Pro and everything worked fine until High Sierra. I have two external monitors that I could not get to work anymore.

What I have now discovered is that if I use a multi-device adapter (e.g. USB-C to HDMI and USB made by Apple), the monitor will not work at all; however, if I use a USB-C to HDMI standalone adapter, I can get each monitor to work. The other caveat is that I have to plug the adapter in "right side up". USB-C isn't supposed to have a "right side up", but if I plug the adapter in upside down it stops working.

I have tried two different multi-device adapters (one made by Apple and one made by Tripp-Lite) and neither work. I have tried two different HDMI standalone adapters (one made by Tripp-Lite and one made by CableCreation) and both work, but only "right side up".

I tried everything else in this thread with no success, but now I have dual monitors working. I hope this may help others.

I was able to fix this issue, the good old way -> remove display link drivers -> reboot -> get latest display link drivers (http://www.displaylink.com/downloads/file?id=1033) -> install new drivers -> reboot and voila my second monitor is now showing up :-).

Hi Eddiemacias,

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

I installed High Sierra on my Macbook Pro and then my mini display-port to HDMI stopped working. I tried every reset and different HDMI cables, nothing worked. Then I found the problem. When installing major updates on Mac's if you leave devices plugged in, as the computer restarts several times during install power surges through your ports can knock out your external devices. Well that's what happen, it broke my mini displayport adapter. after using a new one, problem solved. High Sierra or Sierra can knockout Thunderbolt docks, display adapters or anything connected to your computer. So next time, unplug everything connected to your Mac before updating.

I had the same issue after updated to the lastest macOS High Sierra 10.13 Supplemental Update (Oct 8, 2017) and I've solved it reseting the SMC on my MacPro using the link below:

http://www.idownloadblog.com/2016/02/03/how-to-reset-smc-mac/

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!

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.

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.

The monitor only really runs in one ideal resolution. 1080p I think that it is called.... 1900 x something I forget. The Mac sensed it automatically in Sierra. In High Sierra I have to change the orientation to sideways, which forces it to detect the resolution, and then I allow it to revert and it is great. If I’m in a hurry I’ve become pretty adept at using a mouse on a sideways screen to rotate it back. I have tried picking scaled and saving it but it always goes back to default, which doesn’t work since High Sierra. I first learned these techniques when VGA broke in El Capitan.

I had a similar problem but eventually bought a USB-C to displayport adaptor and connect the secondary monitor via a displayport lead. This is the only thing that worked for me having purchased and returned many different types of leads and adaptors even apple branded ones. This is the only one that I found that actually worked- KiWiBiRD® USB 3.1 Type C THUNDERBOLT 3 to DisplayPort 4K Adapter (DP v1.2a, UHD 4Kx2K 3840x2160, 15.6cm Lead, USB-C to F…

Everything else was unstabled or didn't work at all.

I had this problem setting up a new iMac 2017. I'm using DIV to USB-C adapters. I tried a few different adapters before I found a set that worked. It would appear that not all adapters are made equally. StarTech and another off brand failed to work. I was finally to get it working using a 5-in-1 to USB-C adapter (with no noticeable brand on it).