Big Sur 11.1 External Display Issues!

I'm now in Big Sur 11.3.1 and I'm still having the same problem with my external display (Dell U2715h, 2560x1440, 60 Hz) and my 2017 27" iMac 5K.

The display is connected to the iMac with a USB C to DisplayPort cable and it only works if the display is powered on before I start the computer. If I switch off the display while the computer is running, when I try to switch it on again the display doesn't shown any image. I could see that it's recognized by macOS in System Preferences, but for some reason the display doesn't detect any video signal.

I can get signal again in the external display only if I restart the computer with the display powered on.

Reseting pram, SMC or using different lower resolutions (1080p) didn't work for me.

Never had this problem before with the same display on different older operating systems. I've been using it since macOS 10.12.4 to all Mojave versions in the same computer and I could switch on and switch off the display with the computer running without problems.

Apple Cinema HD 23" (Was working fine on Catalina)

MacBook Pro 16" (2019), MacBookPro16,1

DVI-I to USB-C adapter

After fresh install of Big Sur (11.3.1 20E241) the Cinema HD Display works briefly, then proceeds to turn on/off/on/off....

If your Display Settings doesn't allow you to change brightness is there an on panel control?

I have two displays that my Mac has never permitted direct brightness control for on any OS (High Sierra, Mojave, Catalina, Big Sur): Samsung 4K tv and an LG 27UL600 monitor--both require on-panel or remote settings changes and these work just fine. Display settings brightness only recognizes my LG Ultrafine 4k 23.7" Have you searched to see if your BenQ has new firmware updates for Big Sur?

Download & FAQ | BenQ US

I use a BenQ SW271. There is a button for the brightness on the screen but I just can't change the brightness. Was never an issue before Big Sur...

There is an update for Color Palette but I use i1Studio. That's because Color Palette doesn't work for the Xrite colormunki I use for calibration.

But I don't think this will be the problem?

Maybe it's the cable I use... Not an original Mac cable, could this be it?

FYI, if your monitor speaks the right protocol, there's an app called MonitorControl that you can use that can control the brightness and volume of the non-apple supported monitors. It works great for my Acer ultrawide monitor. It allows brightness and volume control via the keyboard keys.

I downloaded this to a Mac Mini 2018 running 11.3.1 and although I could get it to hook up in Settings > Security > Accessibility to be seen by the Mac when I double click or open it nothing happens. It may or may not work for other users on their Macs w/Big Surs. YMMV--but my on-panel / remotes are Ok for me.

Oh dear! I'm back to square one with my 32" 4k BenQ.

Connected using USB-C to my MB Pro 2019. It seemed to be okay for about a week but since taking my laptop the first face to face meeting in over a year I came back to my home office to find the same problem. The max resolution is 1080p. Awful.

Running the latest update to see if anything changes. Will then reset PRAM, and then SMC to see if anything works.

Forcing me to edit 4K promo vids in 1080p on a monitor capable of much more is unacceptable Apple! Please bring out a fox ASAP.

After the 11.3.1 update, a new behaviour occurred. The secondary monitor works now after restarts, but not if the system boots up. The news are, now, the main monitor is not working after a reboot. This happens sometimes, not constantly. If I reconnect the monitor and change its inputs back and forth, the monitor works again. The Computer is a Mac Pro 7.1 and the monitors are both made by Eizo.

Just updated 1o 11.3 and I'm getting the off/on behavior some other people are describing with my Wacom Cintiq 20WSX. It's very old, I know, but it works fine on Mojave.

Anytime I unplug/plug, it stays on for about 5 seconds but then goes back into the off/on. Same behavior if I edit its display settings in anyway.

I know my own issues have been slightly different than most with both of my identical HDMI displays detected but the completely random swapping of screens & apps on unlock. Updating did not make a single bit of improvement for me, however changing on cable from USB-C/HDMI to USBC/VGA (an option for me that I realize not everyone has) has resolved the screen swap problem. Refresh is lousy on that screen, but at least everything stays in the same place!

I have an LG 32 ud99 updated everything still can not get my 4K resolution since updating to Big Sur you would think with a company as big as Apple they would have fixed this by now about to toss this out of the window disappointed come on you can release all these new products for money but can’t support the avid fan base that has already invested ridiculous maybe time for windows!

Same same. Also intermittent recognition of monitor sound output = infuriating when listening to music or having a zoom conversation when suddenly monitor goes mute. Also, screen still going black... randomly. I've seen these anomalies on other posts so we're not the only sufferers. No suggestions except for Apple techs; PLEASE address these very frustrating bugs & issue an update ASAP!

I switched from using MBP direct usb-c connection to external display's usb-c port, to MBP usb-c -> HDMI adaptor -> external display's HDMI port, then this issue cleared. I guess Big Sur has a bug with usb-c drivers.

In case anybody is wondering, this problem has still not been fixed.

I have a 16" Macbook Pro (2019) - I had zero problems before the 11.1 Big Sur update in December 2020. Since then, my Macbook has not been able to use external displays with via Thunderbolt 3 / Displayport.

I have never had any problems with my TB3 <-> HDMI adapter. The problem is - and always has been - with Displayport profiles over TB3. I am very disappointed with Apple - 5 months and still no end in sight.

Updated to the latest 11.4. My external display still does not work. After disconnecting/connecting my monitor displays video signal for about 5-10 sec. and then goes black and then I receive "no signal input" message.

iMac 27" 5K late 2020, thunderbolt 3 (USB-C USB-C), external display NEC EA271U.