How to fix refresh rate Issues on Dell monitors after Sonoma update

Same issue here with an external 4K Samsung monitor.

My Mac mini (M2, 2023) started recognizing my display again only after downgrading the OS to Ventura from Sonoma.

I strongly recommend downgrading the OS if anyone is facing the same problem.

Mac mini with Sonoma did not recognize my display no matter what I used (HDMI & DisplayPort via USB-C).

i think it is a bug. i also have the same problem with my macbook m1. at first, the refresh rate option was not there. i don't know what exactly made the option appear after i did two (dumb) things;

(1) i searched for the refresh rate option then clicked it, however still encountering the same problem, no refresh rate option appeared, only in the search box.

(2) i plugged the charger and entered clamshell mode (closed my laptop while being connected to the monitor), then started doing random things, afterwards i opened it back and unexpectedly it appeard when i hovered over in the display settings again.

P.S. I am using Type C to DisplayPort adapter to connect it with KOORUI 24E3 monitor (using DisplayPort)

That’s not a solution if an existing external monitor setup worked fine before upgrading to Sonoma.

Thats a transmission issue due to differences in pin outs of USBc cables.

If there were prior common successes using lower bandwidth cables prior to Sonoma then it’s the OS.

ok a monitor full power cycle off and turning it back on has resolved the issue. so random, but glad its working.

Can you try resetting the Dell's monitor settings to the factory ones? and then open the monitor setting and check that DDC/DI is OFF, LCD conditioning is set to off, HDR to off, and USB C prioritization to "high-speed setting" These settings demand less power from the monitor. Then check in Mac screen settings in "advance" section if the Show resolutions as list is toggled on. that's the basic I can tell. If Sonoma breaks something else I don't know. I do have a Dell 4k but I have an m2 Mac without these issues you mentioned. maybe it has something to do with m1? but it's a bit strange.

That’s not very helpful if you’re like me and have Apple Thunderbolt Display. The Thunderbolt cord is literally attached to the display and you can’t remove or replace it.

Everything worked flawlessly for 3 years, multiple OS updates… until the day I installed Sonoma. Issues ever since.

I found a solution. This has worked on my 2018 iMac.

1. Unplugged external monitor and re-booted machine
2. Plugged Monitor in
3. System Settings>Displays>Desktop & Dock> Scroll down to Mission Control. I clicked on various combinations of these options and found switching ON both 'Automatically rearrange Spaces based on most recent use' AND 'Displays have separate Spaces'

These worked for me - Good luck

This happen to me when I upgraded to Ventura. I am connecting two identical LG 27UD58 (Max 3840 X 2160). One monitor cable connected to a HUB and the other monitor cable to the MacMini. I am using:

1. 1. HDMI-to-DP and
   2. USB-C-to-HDMI
   3. (and tried USBC-to-DP).

I did notice improved results connecting both monitors to the MacMini USB-C ports vs. one on the CalDigit Hub, but it was not consistent for months and then started working consistently with automatic updates enabled. Interestly enough with the latest Ventura update one of the monitors goes into night mode (reduced blue light) during the daytime and I do not see any settings that would warrant this.

Is anyone having trouble with the LG UltraFine line of monitors, like these model numbers:

27MD5KA-B, 27MD5KA, 27UN850-W, 27UL500-W, 27UK500-B, 27MD5KL-B, 27UP650-W, 27UL850-W, 27UP80B-W, 27UK580-B, 27UP650-W, 27EP950, 27UL650-W, 27UP850-W, 27UP600-W,

Yup. Did the same. Painful but Ventura works. Multi-user switching also is much better in Ventura. What is Apple thinking?

Does not work over HDMI ... same issue, 60Hz was working just fine on my Samsung 43" QLED HDTV before upgrading to Sonoma. Now I can only get up to 30Hz -very frustrating.

Unplugging, rebooting, NVRAM resets -nothing will restore my 60Hz setting. May go back to prior OS.

In my case, I noticed that I have to keep my MacBook open in order for my external displays to work. If I close the MacBook, the external displays won't work, which is strange to me.

Same issue. Macbook Pro 13-inch, 2020, using Thunderbolt to a USB-C hub to a Dell U2723UE monitor via HDMI. All fine before Sonoma. Now not.

Monitor shows up in the Displays panel, but monitor reports "no signal" and goes to standby.

You don't have to use the built in cable. Just use a TB2 cable connected directly to one of the TB ports on the display.

Some fiddling with the monitor settings did the trick for me!

Me too. I Unplugged the mac magsafe power from the macbook. Then I had the USB C/Thunderbolt going straight from the mac to the monitor. I turned the monitor off and on spamming the button a few times and it just started working inexplicably.