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I keep running into a frustrating situation. Here's what's going on.

Step 1 - I leave my 2019 16" MacBook Pro plugged into an LG 5K Ultrafine monitor. After a while, the screen and the laptop go to sleep. The laptop lid is always closed.

Step 2 - When I wake up the computer, the LG 5K screen never shows anything (it's black). I know the MacBook Pro is awake because I hear interface sounds and I also feel my Apple Watch tap me when it automatically unlocks my machine. No matter what I do with the external keyboard and trackpad, the screen never comes on.

Here's what I've tried:

  • I unplug the computer from the monitor and plug it back in. This makes the screen come back on about 30% of the time.
  • I open the lid of my laptop, wait a while, and the monitor comes on about 70% of the time.
  • I reboot the machine and leave it plugged into the monitor. This works 90% of the time.

Sometimes I get a kernel panic when trying all this and the machine hastily shuts off and I have to boot it up from scratch.

While MacBook Pros have almost always had sleep/wake issues since I first got one in 2007, it's noticeably worse with the 16" MBP. I know this because I also have a 15" MBP for work and it doesn't have these problems with the same monitor on my desk. It wakes the screen right up when I wake up the laptop with the bluetooth keyboard.

Has anyone run into this? Any suggestions?

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The issue has to do with the clock sync. Basically, the Mac "knows" that the monitor is connected (I've verified that EDID data was being received), but since the Mac and the display "won't get on the same page" so to speak, the monitor shows blank.

I'd bet if you were to test this with a Bootcamp install of Windows on the same machine, you'd have no issues. The Windows drivers are just more forgiving than the macOS kexts.

Many times you can solve the issue through hardware by using an active adapter if you are converting the signal (i.e. DisplayPort → HDMI). However, if you're going DisplayPort to DisplayPort, there's nothing the active adapter is going to do to fix it.

You may also want to try powering cycling the monitor (if the power button doesn't work, try unplugging from the mains) while the Mac is awake. This solved it for a number of folks.

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On March 26, 2020, Apple released macOS Catalina 10.15.4 which said the following in the release notes:

Fixes an issue with screen brightness for the LG UltraFine 5K display after waking from sleep

I noticed this and upgraded immediately, and so far, it seems to have fixed the issue for me!

I've been able to plug my laptop in and have the LG 5K screen come up right away without the usual shenanigans I normally have to do to get the screen to work.

Hooray!

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  • This upgrade fixed it from me too after suffering for three months through it. – gae123 Mar 28 '20 at 19:51
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I have the same issues using a 16" MBP (2019) with an LG 34WK95U-W monitor.

I'm on Catalina 15.5.5 (latest as off today). Also Screen Manager doesn't support this monitor. I also couldn't find a way to update the monitor's software.

My current fix is to plug out and in the monitors power cable. Obviously this is not a pleasant workaround.

Any idea where to go from here?

UPDATE
It got better with 10.15.6. Now with 10.15.7 I sometimes have audio problems 🤷‍♂️

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  • I am on 10.15.7 as well - unplugging in and out works sometimes to reset the monitor but I am getting this weird state where mouse clicks / track pad clicks when the monitor does not wake up gets frozen out - I have to restart my entire laptop. 16" MBP 2019 and LG 34WK95U-W as well here is this still affecting you? Have you upgraded to Big Sur yet? (I'm afraid to) – somedirection Dec 9 '20 at 15:33
  • I have two monitors plugged into a docking station on a Macbook Pro 13", and I have this same problem. Either one of the monitors will randomly not wake when I wake the computer after a sleep. Sometimes they both wake, sometimes only one, and it can be either one that doesn't come back. Removing and replacing power to the affected monitor usually cures it. Oddly, using the power button on the monitor to cycle it does not cure it. The Macbook lid is closed. I don't have this problem when I leave it open. But with two big monitors I don't need the laptop taking space on my desk. – jay613 Dec 21 '20 at 2:42
  • @somedirection: yes I have upgraded to Big Sur. So far no issues with my screen. Big Sur did break some programs of which I haven't had the latest version installed though^^ – themenace Dec 21 '20 at 15:29
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I had the exact same issue (16" MacBook Pro + 5K LG Monitor). I download LG Screen Manager app from the Mac App Store, which updated the monitor's firmware and seems to have solved the issue for me.

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  • Thanks for that tip. I checked that and was already on the latest monitor firmware. – Clifton Labrum Mar 27 '20 at 17:23
  • The app sucks, never seems to allow me to manually check or first the update. Does it just automagically allow for the update? – somedirection Dec 9 '20 at 15:39
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I have the exact same problem with a MacBook Pro 15 2016 model since the release of that monitor. This problem is mostly LG`s fault, it is known for years and there are no updates or other attempts to fix this issue. Apple only pushed an update for 2018 models as the monitor was not working at all for those devices. Now we are stuck with these issues for years.

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The problem: The 5K LG Monitor Ultrafine that Apple sold intermittently while they were creating their own doesn't "auto wake up" or stays dead. The MBP sees it enough to produce sound through it, and use the camera, but the monitor never wakes up.

The research: I see hundreds of threads out there with this issue (including https://www.reddit.com/r/MacOS/comments/eqyn5t/lg_ultrafine_5k_doesnt_wake_up/ ) but after hours of reading each one, there never was a fix. Some had success with a reboot or an unplugging of the monitor, but most did not.

The fix: You literally have to use the EXACT same cable that LG sent with the monitor (and) plug it in on the left / rear USB-C port . Watch an old unboxing video ( https://www.youtube.com/watch?v=Snzshdl3hHI ) for example on the monitor, and you can see that the cable has a special little power stripe on it. In fact, the best success is obtained by following the unboxing video to a "T" since the monitor is so finicky that it likes to have the MBP in an open clam before connecting it if it's been off for awhile.

Why: A real thunderbolt USB-C cable doesn't appear to be enough ; I'm guessing that the frequency must be perfectly achievable or the monitor doesn't think it's connected. This is likely needing a 5A 100W cable Gen2, but I didn't even have success with this one : ( https://www.amazon.com/USB-C-Cable-Delivery-Charge-10Gbps/dp/B07MW1ZWP6/ref=sr_1_6?crid=TCZ9QG2K1ZZ&dchild=1&keywords=5k+lg+ultrafine+usb-c+cable&qid=1615671733&sprefix=5k+LG+%2Caps%2C187&sr=8-6 ).

I'm going to search to find out more, but this question was asked so many times in the Apple community and I thought perhaps others may benefit from my hours of swearing ( er, troubleshooting ).

jasonCbraatz

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