External Display not working since upgrading to 10.15.2

[weichsel]

I am using a new 16'' MBP and have upgraded to Catalina 10.15.2 today.
Since the update, my external screen (a 27'' Cinema Display, connected via USB-C/mDP adapter) no longer works.
The screen simply stays black. It is connected an has Power. Sound over USB (connected via Apple Adapter) works, graphics and sound over Mini Display Port is not working.

I tried several reboots, SMC & PRAM resets, connecting to other USB-C ports and booting into Safe Mode. Nothing - the display stays black.
Did anyone else experience similar problems with the latest update?

 

[chscag]

Do you have a spare adapter and cable to try? It could be a coincidental failure of one or the other when you upgraded to 10.15.2. I know it sounds unlikely but you should try swapping those first. Also, and I hate to mention it, but Cinema displays are showing their age; yours could have failed during the update.

 

[weichsel]

You are right, the display is a dinosaur - so it's entirely possible that it is dead now. I will check the adapter first. Seems like my old Cinema Display waited until Apple released their Pro Display XDR before it went black

 

[Nixon506E]

I am also having this issue. Monitor is fairly new and worked right up to the point of the update to 10.15.2. I have also tried PRAM resets and multiple reboots with no success.

 

[Pepe4life]

I encountered this problem too. I’m using the Apple multiport adapter. I had to shut down my Mac, unplug and then re-plug the entire adapter. Ridiculously annoying

 

[rmt37]

!!!!! Yep. I’m using an external eGPU (ATI Vega 56) to power my Cinema Display on a Mac Mini 2018. The update did a shutdown about half-way through the update, and now I have a backlight black screen. I did the unplug, replug thing like I’ve had to do with 10.15.1 but it didn’t fix it. Guess I’m going to have to find a portable HDMI enabled monitor to see if I can at least get some kind of video going. I even tried to access it remotely via VNC, which usually works, but the Mini isn’t even showing up.

 

[Glenny2lappies]

FWIW I use a couple of Cinema displays; one at home, one in the office. I use the official Apple USB-C to Thunderbolt adapter - have one connected to each display.

This works OK

However, I have an issue -- which I suspect is Fusion related -- where the Cinema display is often black after unlocking. Workaround is to unplug and plug back in the Cinema display's thunderbolt cable. It doesn't seem to happen if Fusion's not running.

 

[tommiy]

I've gone back to 10.15.1 for stability reasons. 10.15.1 did not kernel dump on me and 10.15.2 did it twice last night. I can not work with thinking that the machine will crash on me at any one point. Great that I keep back ups because a minor . release results in kernel panics.

 

[weichsel]

Update: I just received a new Mini Display Port to USB-C adapter and this one works with 10.15.2.

So the root cause of my original problem was a faulty mDP-USBC adapter and the problem just coincidentally occurred after the 10.15.2 update.

 

[chscag]

Thanks for posting back. I sort of suspected either a cable or adapter failure. Glad it wasn't your Cinema Display! ?

 

[tommiy]

Given its the holidays I thought I would stuff around with my OS and revert back to High Sierra to see if the brightness, resolution and polling issues associated with external monitors existed back then. Highly successful in that none of these problems exist in HS. Further more my daughter purchased a Mac pro at xmas and it came with 10.14.5. Seems it has no issues either with external monitors. Seems the entire problem started with 10.14.6 with the WindowServer and Nightshift incompatibility with an external monitor and progressed into Catalina with the 3 additional problems upon fixing the Nightshift issue. If there was some process of getting back to 10.14.5 I'd probably try but at present, to get stability, remove the frustration of external monitors changing resolution and the MAC retina going max brightness when its plugged into an external monitor I may just decide to remain on HS. If I do I probably will wait until 10.15.6 or whatever before even looking at Catalina again. 9-10 months of maturing Apple may get around to supporting external monitors again. Maybe 2020 holiday present same time next year.