External Displays won't come back on

I got the same issues.

MacBook Pro (16-inch, 2019) with one LG UltraFine Display 5K, and one Apple Thunderbolt Display.

What works for me as a temporary fix is never to let the displays go to sleep automatically. As long as I put my Mac to sleep by myself, I have not had any issues so far waking up the displays. But its not a permanent solution. Hopefully, the next update will fix it.

The only solution for me is to never let the computer sleep when it is hooked up to external monitors. If I let it sleep for two long it crashes with a kernel panic as others have outlined. If I let it sleep for a little while sometimes I only get one monitor back, sometimes neither, and sometimes it is fine.

This problem is definitely not fixed with 10.15.4.

But I have given up. They will fix it maybe someday and in the meantime not letting your computer sleep is the solution. I cannot believe what kind of quality control this represents. They must have thousands of submitted kernel panics on this.

I've too have this issue and honestly thought it was everything from the displays to using the Vertical BookArc to the Kingston Nucleum USB-C hub.

I started with my original set up for my 2015 MBP which was a 27 inch Thunderbolt display and 23 inch Cinema Display. It worked sparingly and so I swapped out the older 23 inch Cinema Display for a 27 inch Dell thinking the HDMI to USB-C connection would certainly be better than the DVI to USB-C adapter...it didn't matter one bit.

Every configuration of cable/port and hub result in basically the same result. Anything longer than 1+ hour of sleep either shuts down the MBP completely or renders one of your displays unusable. Sometimes it's active, but the screen is black, other times it's not even responding.

I've tried the power cable into the USB-C hub, into the DVI-USB-C adapter and the solo. Same result each time.

I've put both displays on the left and right side. Same result, always.

The only success seems to be manually putting the computer to sleep and/or checking "Prevent computer from sleeping when displays are off" via the SysPref.

Even the software update on 3.31.20 has rendered nothing new. As a long-time supporter and user of  products this has been the most frustrating issue I've ever had.

Similar to others, during the day when I return to my laptop I am able to wake it from sleep and the monitor switches on without issue. Overnight however, I find the MacBook has restarted with a report containing the following:

"panic(cpu 0 caller 0xffffff800ae91b2c): Sleep transition timed out after 180 seconds while calling power state change callbacks. Suspected bundle: com.apple.iokit.IOGraphicsFamily. Thread 0x2f233."

I have an ASUS PB277Q external monitor - connected via HDMI.

This monitor worked flawlessly on a Thunderbolt connection to my MacBook Pro late 2013.

Catalina 10.15.4

16-inch 2019 - 2.6GHz 6-Core i7

32GB Ram

Intel UHD Graphics 630 1536MB

Since the latest update, I haven't been crashing. Using the "magic" touch bar to change the brightness on the monitor that stays dark upon waking brings it back on. So it has been better for me, but still not right.

Update: on my troublesome 16-inch, I have now activated Screen Sharing.

From my other macbook I can remotly log in to the 16-inch, when it has crashed after not waking up.

For me at least, the 16-inch has indeed woken up. It's displaying the screen where I'm supposed to enter my password (which is strange - i have that option turned off in the Security Settings).

From what I can tell, the 16-inch is working, it's just that the graphics is crashed and the internal display is black. The Activity monitor ("Energy"-tab) sais that I'm using the "high perf" graphics card, which is correct since I'm using an external DELL display. However, when I disconnect the external display, the Mac will not switch to "internal". It still sais "High Perf"

Opening System Prefernces and going into "Displays" shows that - even though the external display is disconnected, I only get options for my "DELL"-screen. I don't even get the "Arrange windows"-tab, meaning my 16-inch is not aware about the lid now open.

The only option for me really at this point is to choose "restart" from the apple menu, and allow the 16 inch to reboot.

Has anyone else remotely logged in to the "crashed" 16-inch?

i have been using a GAEMS M155 monitor connected via Aukey UCB C adapter w/ HDMI out that was driving me crazy because it would randomly work and then not work when connected to my new macbook pro 16 via HDMI (my ext monitor would show "low or weak signal"). it was super inconsistent and i tried everything to troubleshoot- new cables, testing monitor elsewhere, etc.

finally stumbled upon these forums, tested a theory i read by one of the posters here and wanted to share what worked for me to get my ext monitor to work consistently: unplug and then re-plug in the usb c power cable.

this causes the mbp to flicker and i guess sense what is connected to it and supply power accordingly. this is essentially what i do now for this particular monitor every time it decides it doesnt want to display when powering, no need to shutdown or restart anything. hope this helps someone!

I decided to install MacOS from scratch again thinking I could roll back to an older OS, that did not work out as I forgot Apple does not allow this on new Macs, so reformatted HD and did a clean install of Catalina. Since then I have had no monitor problems at all so maybe I got lucky. If I'm honest the MacBook never hard crashed when I had the monitor sleep problem, all I had to do was disconnect the monitor from the thunderbolt port and reconnect again to get things working.

This has been going on for far to long to be ignored by Apple anymore. Has anyone here contacted other channels to see if they want to report on this problem. Maybe if we can drum up some awareness on the issue Apple might get this sorted out because it's been going on for too long in my book. At this price point we deserve a better service.

I am having similar problems with the 2019 16" i9 and a LG 21.5" 4k Thunderbolt Display. I thought, as well, that 10.5.2 fixed it but it has resumed again.

The issue occurs in two ways:

1. On wake from sleep, both screens flicker in turn, quickly, and neither one takes. The Touch Bar flickers as well. Disconnecting the screen is the only solution.
2. On wake from sleep, the laptop has forgotten the external display and only activates the internal screen. However, USB devices connected to the external display continue to function.

I have tried disconnecting devices from the external display, plugging and replugging, etc. The only thing that works is to restart the MacBook Pro. I had been using this very same setup with a 2016 MacBook Pro prior to this with no issues.

Having the exact same issue! Spent nearly $5k on this 16" MacBook Pro and this has been going on since I got it in December, Apple this is UNACCEPTABLE ! ! !

Called Apple support only to have the m tell me it's most likely a hardware issue and I need to go to a repair facility, I told them when I got this MacBook in December and this started happening I exchanged it and got a different MacBook shipped to me only to have the same issue occur, and considering everyone else that is experiencing the issue, it's OBVIOUSLY NOT A HARDWARE problem.

Basically when the MacBook goes to sleep for a few minutes I can wake it up and the external display kicks in, but it seems that if it goes to sleep for an extended period of time when I wake it up the external display doesn't kick in and the MacBook display starts flashing until I unplug the Thunderbolt 3 HDMI adapter, if I plug it back it in it just starts flashing again and I am forced to reboot.

For now I have unchecked "Prevent computer from sleeping automatically when display off" and "Put hard disks to sleep when possible", hopefully that works, but this is NOT a fix for a $5k MacBook.

Lets hold Apple accountable and hopefully 10.15.4 fixes the problem, but I'm not holding my breath as I didn't see this issue addressed in their 10.15.4 Beta release notes and I was hoping 10.15.3 would fix this issue and it did not, still hoping for resolution in 10.15.4.

If anyone figures out a solution please post on here and I will keep this thread updated as well when 10.15.4 comes out, again for now I've basically disabled sleep, it's just insanity to me that I have to do this on a MacBook of this caliber and price!

I had the first kernel-panic crash since updating the 10.15.4. Unlike the typical conditions during much of last week when my MBP16 was problem free, this time, I had all 4 Thunderbolt ports engaged (one for LG UltraFine 5K, two for external HD, one for the Belkin USBC extender), and the Settings (Energy Saver) was set to Defaults. Other than that, nothing unusual. Maybe I have to go back to prevent it from going to sleep and/or stopping HD...

[looking at the system log, the crash seems to have happened at 2h29m pm, and before then for about 40 minutes, the computer was busy generating:

"Mar 29 14:28:31 MBP-16 com.apple.xpc.launchd[1] (com.apple.DumpGPURestart): Service only ran for 1 seconds. Pushing respawn out by 9"

every 8 or 9 seconds or so. No other messages, but these and then BOOM.

All these issues are always related to the GPU as you can see on your message: "com.apple.DumpGPURestart"

Thousand of users are having different problems, all related to the discrete GPU.

Hopefully AMD and Apple will fix it on the next update, because it's becoming more and more difficult to work on these machines with all these issues.

Having the exact same issue as everyone else in this thread. So incredibly frustrating, especially since this is a brand new 16" MBP i9 with very high specs that cost a fortune. I'm using an ultra-wide LG 34" monitor and a CalDigit TS3 Plus Thunderbolt 3 Dock to plug in all my other peripherals (Apple keyboard, wireless mouse, etc.). Please keep in mind that this is supposed to be a premium dock and one that should be "Apple-approved" as Apple themselves sell it on the website.

To reiterate the problem others have listed in the previous 8 PAGES, my computer won't wake up again if left plugged in to the external monitor for too long without activity. My laptop apparently goes to sleep, seems to have a crash occur, fans kick in for a second or two, and then I have to unplug from my monitor from the hub and do a hard power reset for the computer to come on again.

My computer has been running 10.15.3 but just recently made the update to 10.15.5. I will give this a try and also try switching the power supply to use the MacBook's EVEN THOUGH CalDigit specifically advises against this and you are supposed to use one of the Thunderbolt ports to connect to your Mac since the dock itself is supposed to supply the power.

Please Apple, look into this as soon as possible. I loved my previous MacBook Pro because of all the things it let me do as a creator on the go, but after just owning this one for less than 2 weeks, it's leaving a bad taste in my mouth after spending so much money on it.

I see a brief yellow flash sometimes. I'm still seeing this issue after disabling power nap. Crashes almost every time i plug it into an external monitor and seems to have gotten worse with 10.15.5, not better.

My company's IT department reached out to Apple and was told that they are aware of the issue and have been for some time but no solution is forthcoming. The exact words he used is "they are stumped". Awesome.

Further update: switching to the left ports does no good, it will eventually happen there as well.

What is curious is that I was getting the flicker on the left side, so I switched the cable to the right, and that worked. For awhile. So the port side in my case makes no difference.

I have noticed that having my external drive plugged into the external display USB hub seems to make the issue happen more often, but it will happen without it, too.