16" MacBook Pro Doesn't Wake Up Screen on LG 5K External Monitor 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?
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&#39;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.