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

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

In my case, it was the monitor. I had to go into the menu and change the color profile to something else and it cleared right up! Just putting this in case it helps anyone down the road. M1 Sonoma, 1080P Asus monitor on HDMI.

Same issue. Upgraded to Sonoma and had a hard time getting two monitors to work. I had to go through my 5 docking stations (Yes, I have 5) from testing on Mac M1. Only 1 worked if I connect one monitor to DisplayPort, one to HDMI and set the DisplayLink software to enable experimental 3008 x 2560. If you don't enable the experimental option in DisplayLink it won't work. So try connecting one monitor to HDMI and one to DisplayPort. You may need to try a couple different docking stations which I know is crazy. All my docking stations worked on Ventura no problem and after the upgrade, major problems.

It looks like the display kernel was rewritten because when you boot, the external monitor does show the boot screen and what is happening at boot which is awesome. Ventura could not do this and I always had to open the laptop to login and let the DisplayLink drivers load.

I think this is heading in the right direction and they just need to work out the issues. A driver rewrite is always tough but it needed to be done to be able to see the boot information on the external monitor. I am sure they will fix it but it is frustrating for the time being.

It happened at the worst time for me too because my PC laptop crashed and I needed the Mac while my PC was being repaired (the Mac is my backup and travel machine) and I could not get the displays to work and I absolutely need two monitors as I program and do system admin work.

Don't go too crazy with trying to get your monitors working until they fix it.

[Edited by Moderator]

JFC why did I upgrade when everything was fine? Now my HDMI display not recognized. What fixed it for me was Shut Down MBA, unplug monitor, restart MBA, plug monitor in. It’s working. For now.

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.

I had a similar issue, USBC cable only showing 30hz. In my case it was a cable problem, I had to use a specific combination of cable connectors facing up/down when plugging to get the 60hz (no reboots)

I wish people would stop posting these non-compliant cable solutions when clearly there is a persistent output issue with 14.0 - 14.1.1

Those of us with Apple branded or known compliant displays like the LG Ultrafine that were sold through the Apple Store have experienced the same wake, detection, resolution, and framerate issues as display users that weren’t sprinkled with magic approval dust.

I had a very similar issue.

McBook Pro 14 inch with Apple M1 Pro Chip running Sonoma 14.1.2

My LG UltraWide Monitor dd not have the right resolution (2560x1080).

Every time I disconnected the HDMI cable and re connected it, different options appeared, so I ended up rebooting, disconnecting everything and reconnecting it and it fixed itself.

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,

i just got a new adapter. Problem solved. Good luck.

Much of my monitor problems went away after replacing the cable with an apple cable 240W USB-C Charge Cable (2 m) - Apple. Doesn't mean this will help you but it could.

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

I found a solution for my case (MacBook Air M1 8GB 256GB).

"Seven troubles - one reset" =)

I have performed 2 reboots and one shutdown of the mac, and now everything is fine.

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.

I have had nothing but hassle with my two LG monitors when using a hub and the display port on that hub. I finally sprung for a new cable and Caldigit hub and so far I have only seen one external monitor hiccup once but finally behave as expected.