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

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 the external display flickering problem on my M1 Air since I upgraded to Sonoma.

I cleared nvram: sudo nvram -c

I pulled all of the devices connected to my LG 24" Ultrafine and had less problems.

It acts like a Thunderbolt port is bad on the display so I switched to the other one.

The affected tbolt port on the display I know is fine.

M1 Pro that's still on Ventura runs the display completely fine with devices fully populated to the LG's internal hub on either tbolt port.

Similar issue here any suggestions?

imac 27” 2020

thunderbolt display

for years they’ve worked flawlessly, after Sonoma upgrade every time my imac goes to sleep overnight and I wake it up the next day - the Thunderbolt Display is not recognized. I restart and everything works.

not ideal. :(

On my MBP/M2 I had to shutdown the MBP (not restart) (apple menu/shutdown). I waited 30s to make sure it was shutdown then powered on from the power button. Since then the external display is recognized via thunderbolt/USB-C cable, which also charges the MBP. It is recognized even after I put it to sleep.

I just fixed this issue. The solution was to purchase a new USB-C 3.2 cable that supports 40 Gbps and 240 W of charge.

My experience:

July 2023: Purchased a certified USB-C 3.1 cable that supports 10 Gbps and 100 W of charge. It connects beautifully to my external monitor.

Early Oct 2023: Get a laptop with Sonoma. It does not connect to my external monitor. I follow all the advice on this thread, and nothing works. I purchased the above new USB-C cable, and it connects flawlessly.

Note: Be very careful to get a USB-C cable certified for 40 Gpbs of data and at least 100W of charge. I had to purchase multiple USB-C cables before it would work (I'm currently returning them).

Yet another reason why I loath OS updates.

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.

I also have not had problems with my Caldigit TB3 hub. My OWC travel hub is a different story and when I tried to open a claim they told me that Apple video glitches on a hub is a well-known problem and that they would not allow the claim.

I have an adaptor Hper that has two HDMI ports and before I installed Sonoma 14.1 in displays I could see my two external monitors and my mac pro 13in M1 2020 - the adaptor has a thunderbolt and plugs into one on the computer. After update and installation of Sonoma...on or in the displays I only see one monitor and my macbook...I have tried unplugging power and cords and sleep mode...etc...nothing changes...one screen is black and the other works....how can I fix this?

I'm using a M2 Air with a Dell 27" 2k monitor and under 14.0 I had to unplug and plug back in after reboot and it would come back on. Under 14.1 I only have to turn the monitor off and back on to get the monitor to come back. What I just noticed though is that the Logitech webcam that is plugged into the monitor USB-A port is no longer recognized no matter what I do. Apple has seriously screwed the pooch on this one.

Yes same. Not a webcam here but an external hard drive… it won’t mount or dismounts or randomly ejects improperly the time since Sonoma 14.0 update. So frustrating I was fearing it would eventually cause the drive to go bad.

BUT…. Notes in Sonoma 14.1 say it fixes that issue. And so far a few days in after updating I think, it’s not ejected once. Crossing my fingers...

Wish I could same the same about my M2 Air, I upgraded from Ventura to Sonoma on my M2 Air and have had this problem ever since. Mater fact I discovered today that 14.1 has actually taken a step backwards. Not only does my monitor not work when I reboot but the webcam that is connected to the USB-A port on the monitor is no longer recognized at all. Nothing I do brings that back.

I thought a well designed HUB like Caldigit would help but I too am having issues with many third party devices particularly my Dell and LG monitors. I have four USB-C in my Intel MacMini so I am getting by but with my M1 MacMini I don't have the luxury and often have to reset my HP monitor by turning off and on for the M1 to recognize it.

Same issue, I cycled the power on the monitors (hard cycle, by pulling the power cord) while still connected to the usb c/thunderbolt port. When the monitors came online I received a prompt from the Mac book to connect external displays.

I have two seemingly identical Dell monitors (S2719dc) -- one purchased in 2019 and one purchased in 2020. One works and one doesn't after the upgrade. I tried switching the cables from the monitor that works to the one that doesn't, with no success. This means it's not a USB-C cable issue.

I've powered on and off the monitors. Restarted my machine multiple times.

Is there another path forward? Or do I need to wait on Apple to do a patch to the OS?

2020 27” iMac and Apple 27” Thunderbolt Display

Wow. 14.1.1 just regressed. 🤦🏻‍♂️

14.0 was terrible. Apple Thunderbolt monitor would disconnect and my external hard drive would eject improperly daily.

14.1 both worked well. Did not happen at all. Monitor and Externals stayed connected

14.1.1 monitor and externals disconnecting randomly again.

awesome Apple. Great job, I’ve literally been using Mac since 2008. Leopard then Snow leopard and every major OS since I’ve updated instantly and really been seamless. UNTIL Sonoma.

What an absolute sh!+ sh0w