16" MacBook Pro Doesn't Wake Up Screen on LG 5K External Monitor

Solution 1:

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.

• External monitors show blank screen until restart

• MacBook Pro detects syncmaster (monitor) but doesn't display

• USB-C to Displayport cable or adapter

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.

Solution 2:

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!

Solution 3:

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 🤷‍♂️

Solution 4:

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.