External Display not working after 10.13.6 update

to get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, no data will be sent to the display.

This query is only sent at certain times:

• at startup

• at wake from sleep

• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go

• on invoking Option-(Detect Display) button in Displays preferences

so try doing some of those things and see if the display comes alive.

Modern Displays with multiple ports are sometimes busy scanning the other ports, looking for an input, and miss the query from the Mac. They need to pay attention to the port you are actually using, or they will miss the query.

Some displays have On-Screen Display settings that can be used to tell the display a computer is attached on a certain port, or a certain port should be highest priority. Changing those may make your display more responsive.

I'm seeing the same issue with my brand new secondary Dell U2718Q 4K display (hooked up to my 2013 Mac Pro, primary display is a 10-year-old 30" Apple Cinema HD Display). The monitor works really well for me, except for wake from sleep (even if the computer itself isn't asleep, just in screen lock mode wherein the displays have gone blank/idle).

My workaround so far is to "Detect Displays" after logging in. The key is to do so while the secondary Dell display is still searching for a signal. If you wait too long, the Dell display decides there's no signal and goes back to sleep.

Detecting displays in macOS can be a bit cumbersome, as shown in this Apple support article:

https://support.apple.com/kb/PH25173?locale=en_US

So, I downloaded Display Menu from the macOS App Store and paid for the in-app purchase. This gives me the ability to access the Display Menu app's functionality via AppleScript. I wrote a little AppleScript that tickles Display Menu's Detect Displays functionality and run the script just after logging in (via Keyboard Maestro). Works quite nicely for me as a workaround.

I've tried all these and the only one that "works" is re-seating the display cable while the machine is powered on. I had no issues on 10.13.5 with my external Dell U2718Q but as of 10.13.6 the display no longer works (black display) but is *detected* in system preferences > Displays.

Another side-effect after this .6 update is that now my iMac's screen and the external Dell monitor don't go to sleep after I lock the iMac.

I have the same issue, also with a Dell U2718Q connected via a DisplayPort Cable, however mine is for an iMac (Retina 5K, 27-inch, Late 2014) running MacOS 10.13.6. Like the OP, mine worked prior to the .6 update. Either reseating the cable, or powering the monitor off/on, brings it back.

This is happening to me as well, I have an external Dell 4k hooked up to my 2015 Retina iMac 27. Worked fine for all previous versions of 10.13, just not 10.13.6. It's annoying to have manually turn the monitor off and back on for the OS to see it again. (and move half my windows back)

This has started happening to me too after upgrading to 10.13.6 - external Dell display connected to 5k iMac turns off after waking from sleep, and none of the above options get it to turn back on except restarting the computer. This is very inconvenient

I've found a solution that seems to be common across most of the affected external displays!

Check your model monitor for the exact process, but there is almost always a way through the monitor's settings to disable "Monitor Sleep" or other "Power Saving" features. Upon disabling said features, a simple reboot was all that was needed and I haven't seen the issue again.

Now this is a problem that was introduced as of this point release from Apple so I wouldn't consider this "Solved" by any means - this is a workaround.

Hi Geoff,

This looks useful. I have a DELL U3014 and have the same problem. I have the new 2018 13" MB Retina (10.13.6) and am using a USB-C to displayport cable. I have downloaded DisplayMenu and can pay for the $2 paid in-app purchase. Would you be wiling to share the AppleScript that you use to tickle the Detect Displays functionality? I'd really appreciate it and so would others who are running into the same issue. What does Keyboard Maestro do? run things after login? How does one configure that?

Thank you in advance!

I just recently had this issue and it turns out it's an issue with how DisplayLink works in MacOS 10.13.4 - 10.13.6. The solution is to downgrade to DisplayLink 4.3, which will only let you use one external monitor. OR you can upgrade to Mojave and install DisplayLink 5.0 which gives you up to 3 external monitors. The description and fixes are detailed here:

https://support.displaylink.com/knowledgebase/articles/1849327-important-informa tion-on-macos-10-13-4-10-13-6-u

I followed the instructions and now have one of my two external monitors working again. I'll be upgrading to Mojave soon so I can get both monitors back.

Regards,

Frank

Interestingly, version 4.3.1 is available today. Neither it nor the predecessor helped my problems on my 2017 MBP 15" Touch Bar model. (This has not been my only problem, so I may soon visit the Genius Bar.)

larrypang-

what did you do to make it work better?

Also have this issue with my triple monitor set up. Basically I have to disconnect/reconnect the cables every morning.

Read this:

https://support.displaylink.com/knowledgebase/articles/1849327-important-informa tion-on-macos-10-13-4-10-13-6-u

Regards,

Frank