MacBook Pro 16 external display issues

Mr. Bennet-Alder,

I have read your responses in this thread and they seem almost designed not to help with the problem. This is an issue that is recurring for every single MBP16 owner I know and there are several threads on this on the support forms. (Another is here: https://discussions.apple.com/thread/250931552). It does not matter what adapter is used, what monitor is used, etc.

And yet you talk about RF interference and suggest basic items like Detect Displays.

From everything I can tell (from log files from the associated crashes this bug causes if a machine is left to sleep for long enough), this is a memory leak/display driver bug that is either AMD's or Apple's fault. No matter the fault, it is up to Apple to get it fixed and I'm flabbergasted, having been an Apple user for over 30 years, that this has been allowed to sit for four months without fixing it.

The number of crash reports that have been sent on this has to be in the thousands, just based on the ubiquity of the problem and the effect it has on any user with an external display. I would bet a hefty proportion of people buying a 3k laptop use external displays.

I check these threads multiple times a day hoping for relief. I am hopeful that the next turn of Catalina will fix this. But the idea of spending an hour on the phone with Apple tech support so that they can not solve the problem, which can only be solved by an OS update or maybe even a firmware update, is not something I'm willing to tolerate.

Apple really needs to fix this for its most loyal customers on a flagship product.

Just checking -- you are not trying to daisy-chain these displays off a single ThunderBolt port, right?

That has never worked well. For reliable operation, each display should be on its own ThunderBolt port, if at all possible.

Just read in another thread to turn off everything in Mission Control. I don't use MC so I'm trying that. And turning off hot corners too.

I have the same problem. I have tried 2 different USB-C Hubs and on USB-C to HDMI adaptor plugged in to my 2019 MBP 16 inch and each of them have had problems where after sleep, (this is not every time, just sometimes or after the machine has been on for a while) neither screen will come up, or just flash off and on. As of now this has been only when they have been attached to the left side USB-C sockets. When I move the adaptor to the right side the screens are able to connect, or if i reboot the MBP it will work again from the left side.

I have a MBP mid-2012 13" External Apple Display HD 23" (old). Everything worked fine with High Sierra for about 2 years, then I updated to Mojave and the black screen started intermittently.

I recently installed a 2T SSD and installed Catalina 10.15.4 on this brand new drive. Did not migrate anything - fresh install of all apps, just copied over a folder full of my work from old hard drive.

Since Catalina I can get a couple hours or 10 min with the black screen. I really think it has something to do with Catalina as I've been reading up on this A LOT on all different forums. Different models of Apple laptops, but all seem to be on Catalina and all get the black screen.

Like many of you I have to hard reboot to get it back up. I've reset everything, checked firmware, Safe Mode, hard ware diagnostics, AND I have 2 other monitors besides this 23" that are both different makes and models and brands it does the same **** thing. I've tried many different cables, bought new cables and nothing has changed.

This morning I turned on mirroring with the HD Cinema Display being primary (someone here said they made their MBP primary but that didn't seem to work for me). I have to leave my MBP ajar so the screen is still on but it's been about an hour now and the HD display is not flickering.

This is a ridiculous fix, if it is a fix.

Yesterday I walked away from desk for 2 hours, come back to a report from a crash and reboot with kernel panic data. I'm convinced this is a Catalina issue.

WAIT - it just blacked out again and I'm back on my MBP but I didn't have to hard reboot. That's one thing but this is severely interrupting my work flow and very, very annoying.

Different results from different sides suggests a possible failure in the ThunderBolt chip that drives that one side ports.

I have been using my LG 38UC99 display with my old Macbook Pro without any issues. I recently switched to the new 16 inch Macbook Pro and now when the Macbook wakes up from sleep (most of the times) the display won't work. Switching the display port to a port on the opposite side of the Mac solves it sometimes, but most of the times I have to restart the Macbook to get the display to work. Otherwise my Macbook display keeps flashing while there is nothing on the external display. Looks like its trying to switch between the Macbook display and the external display on and off. Not sure how to solve this issue.

I have the same problem with external display turning on and off. I use CalDigit TS3+ connecting to a 4k and a 1080p display. When I enable mirror displays, all displays turn off and on. The internal display turns on first and the other two follow later. Resetting nvram and smc does not resolve the issue. I first thought it was the problem of TS3+ so I ordered a replacement. But the issue is still there. Another issue that display won't turn on after MacBook going to sleep is discussed here: https://discussions.apple.com/thread/250888931?page=1

Exactly the same issue I am facing! I have tried everything I can find online. Nothing has worked so far. Currently I am using an OWC Thunderbolt 3 Dock to connect the monitor. This seems to help a bit in the frequency of the issue but didn't solve it.

I am having the exact same problems as you (gablebt) and ahmedfromsingapore, wherein the external display simply is not detected upon waking the MacBook Pro 16" up from sleep.

I'll try Grant's suggestion below and report back, but this does appear to be a problem with the new MBP, because the same adapter, cables work with my old 2015 MacBook. Changing adapters, cables and monitors did not help.

While our symptoms are slightly different from what was described in mamrotek's original post, they seem to be very related in that they all involve the new MBP 16".

Yeah, I think it's a major issue. I went for a few weeks and did not experience it, and then it came back with a vengeance. After the computer sleeps, it won't reengage the external monitor. Happens with two different monitors. One with Thunderbolt support, and one USBC to displayport. When it happens, I either restart or just have to use laptop only if I don't have time to restart. This is a HUGE Macbook Pro 16 problem I wish Apple would acknowledge and test for.

I did. But looking at this thread, and others around the 'Net, it looks like there's an issue with the new 16" model and external monitors. I'll probably register another ticket with Apple on Monday in case it does turn out to be hardware and I'd be entitled to repairs or replacement.

I agree that there continue to be unresolved issues with MacBook Pro 16-in ability to support large external displays and stay cool.

My way of attacking complex issue is to attack the items that you know to be a problem first. Once the more obvious issues, like EMI/RFI interference and not following the expected procedures are eliminted from the list, then sometimes the remaining symptoms coalesce into a clearer descrption of the issue, and can be solved.

I have never suggested, "do this and all will be well" when it comes to MacBook Pro 16-in issues. My suggestions for improvement are valid, but they are no cure-all. You may object to my suggestions as simplistic, more like "make sure it is plugged in" but if that suggestion occasionally solves a user's entire problem, I will not stop suggesting it as something to look at.

• "Flashing on and off" is unlikely to be a software or Driver issue.

• "Screen stays dark" is sometime attributable to not following the guidelines for making the Mac send a query, and the display to respond.

If problems persist after you try some suggestions here, then Readers should contact Support, using the link at the top of every forum page (when accessed by computer-based browser). Apple is not here and is not monitoring these forums except to keep order and make certain that complaints do not go unresponded to after days.

Your mission, should you choose to accept it, is to NOT allow the first responders to dismiss your complaints as "solved" ,but insist it is NOT solved and you need a bug report filed on your behalf and/or continued following-up from higher experts until actually solved.

Same problem here :-( but with possible new information.

I haven't read the whole thread, but I can confirm it doesn't depend on the monitor/cable/adapter. I'm using 2 monitors, and after waking up only one works, if I detach/attach it it doesn't work. If I detach both monitors and attach them in reverse order then the monitor that was not working starts to work and the one that was working, doesn't (no matter to which port I attach which monitor, only the order in which I attach them matters, first one works, other does not). I don't know if this helps/inspires somebody.