External Display USB-c Monitor issue

In the second half of the day my problems worsened. Occasionally when unlocking my MacBook after waking it and the monitor both screens would flash pink and the machine would crash and reboot. This happened probably 15 times or so throughout the afternoon as I tested waking my setup with different docks and cables. I’ve yet to experience this without the monitor attached, and also haven’t had it happen again since switching to a DisplayPort cable from my dock to the monitor. The other output problems still persist with the new cable however. We’ll see how tomorrow goes.

When connecting a NEC MultiSync PA322UHD to the Mac Mini M1 (USB-C to DisplayPort with a high-quality, direct cable) I have the same problem, I only get 30Hz (on Big Sur 11.0.1.). My MacBook Pro 2015 does 60Hz over DisplayPort on the same monitor. Apple Support told me to "contact the manufacturer of the monitor to ensure it's compatible". Not very helpful...

I had this problem this morning with my new Mac Pro.

I solved like this.

Clicked on the Apple>Displays>Option+Click on Scaled under the list of resolutions tick on "show low resolution modes" and click the desired size, under Rotation a new drop down menu appears "Refresh Rate" this will give you the option to pick 60 Hertz or 30 Hertz.

I hope this helps you or somebody, I was almost going to return my Mac Pro or return my new Monitors.

Good luck!

I have kind of the same issue. New macbook pro with M1 processor and 34" samsung curved monitor on Big Sur 11.01.

When I plug in my thunderbolt 3 cable the external monitor supports 100 hz. But when I restart my laptop from sleep the system switched my monitor back to 60 hz and I can't select 100 hz anymore. If I then remove the thunderbolt cable and plug it back in the 100 hz is available again.

Looks like some sort of bug.

I am having a problem with my M1 MBA recognizing the external monitor connected to the second USB-C port on the laptop. One strange fix is this: I have an Anker dongle connected to the power USB-C port. If I disconnect that dongle, the Mac is much more likely to recognize the display. Then I can reconnect the dongle and it continues to work. Weird and annoying. One theory is that the mere presence of the unused HDMI port on the dongle is confusing the Mac about where to look for a display. Yes, I am aware the M1 MBA supports only one eternal display. I am not trying to use 2. I am referring to an unused HDMI port.

Hey not sure if this helps at all but I have an LGHDR 4K ultra fine monitor that I use as an external with the 13” mbp. I had the EXACT same issue (pink flash and all) when I used the thunderbolt port on the monitor, if I switched and went to just plain ol USB-C it worked competent fine, no crashing at all and still charges the MacBook (not as fast but it works). The only issue I have still is trying to wake the external display. It’s 50/50 if unplugging and replugging will work, if that doesn’t then I need to restart. Pain in the *** either way but definitely better since I stopped using thunderbolt 3.

I have just bought a new MBA M1 and now it's working fine with my external monitor LG27UL550 in 4K@60 mode via USB-C-to-DisplayPort. Big Sur is 11.0. I won't upgrade it anytime soon as I think this problem about versions above 11.0. If you have Big Sur 11.0+ try to downgrade to 11.0.

I have been trying to use an Anker PowerExpand 12-in-1 Power Delivery Media Dock with HDMI. I have found that when I connect the dock after each Power up of my M1 MacBook that I have to power cycle the dock before the HDMI signal begins working again. I've replaced the dock with the same model and still having the same problem. I dont have this problem with a small USB C to HDMI adapter from Anker as well though so I'm not sure if its the computer or the dock just doesn't support the M1s. I can't seem to get an answer or figure out how I can troubleshoot more.

I give my experience too :

mba M1 + LG 4k via usbc, macOS 11.0.1

Most of the time when I wake up mba from keyboard or mouse, screen doesn't wake up

And sometimes after screen wakes up, resolution is not the one I set (wrongly selected natural resolution), I have to go back to settings and get back to 1440p manually (1440p doesn't have effect at 1st try, have to select an other one and then select 1440p...)

Quit boring

I have 3 Macbook Air M1 (base model), all connected to its external LCD monitor. So, basically 1 MBA connects to 1 LCD through 1 USB-C hub. They all have similar issues. On the other hand, my old MBA (2013 mid) does not have any of the following 3 issues.

The 1st issue is similar to yours, slow start for the external LCD after wake up. This happens every single time.

The 2nd issue is, from time to time, the external LCD turns to all black for less than a second, while the MBA's display still on. This happens like once or twice a day.

The 3rd issue is most server, around once in a few days. It goes beyond annoying. Both the external LCD and MBA's owned display turn to pink flash then crash and reboot. Sometimes it doesn't have anything, directly jump into reboot. The problem is, it is unpredictable. It can happen anytime without any symptom.

I just got my new Macbook Air M1 with Big Sur 11.0.1, and connect usb-c to usb-c of LG 49WL95C-W. I used my Apple usb-c cables, I can't get the connection to LG monitor. After I used the original USB-C cable coming with LG monitor, the connection is ok, and ONLY on the top usb-c port of the left on Macbook Air M1. Not working with the second port of usb-c.

In summary, the USB-C port of Macbook Air M1 and the USB-C cable all come to play. The lesson is use the 1st usb-c port, and use manufacturer's USB-C cable.

Hopefully, my experience will help some of your situation.

I have a similar issue mba m1 using usb c to a dell curved. once it sleeps the bt kb will wake the laptop but not the external monitor. I have given up calling apple support they totally ignore the issue. I open the m1 lid, wait 5 seconds for the monitor to come on, close the lid and continue working. on the plus side homebrew, printer drivers, scanner drivers etc are working on m1. transmit is arm native, etc. so taking a dive into arm knowing it wasn't going to be perfect isn't as bad as it could be.

I used LG 49WL95C-W to connect through USB-c cable provide by LG. The connection is OK, and it can wake up by mouse or keyboard after overnight's sleep. So far I am happy. Talk with your display manufacturer to see if they have recommendation.

I agree that it's unacceptable, though I don't regret M1 purchase. I have a similar problem with my Intel Mac Mini, though it usually does not take all day. Restarting computer, restarting monitor, unplugging and plugging the HDMI, that sort of fiddling usually fixes it and it pretty much stays fixed until I need to reboot. It's a serious product issue.

my LG screen connected via usb-c now wakes up after touching keyboard or mouse since 11.1

half of the problem solved for me...

other part unsolved is sometimes it wakes up in the wrong resolution, have to fix it manually through settings