External Monitor Issue After macOS Sequoia 15.1.1 Update

Since two days my primitive graphics adapter works well. Your link, TxPomeroy, wasn‘t helpful for me as Amazon unfortunately doesn‘t deliver it to Germany.

I‘ll await 15.1.2 now, in the hope, Apple will repair this bug soon…

Thanks for this! Quick question: are you only running one external monitor, and not multiple? I was able to run 2 before, and with the update, now only one works, and only one is detected by my mac. No issues with my DELL windows laptop.

Having the same issue here, there is a dead zone on my external monitor, upper left corner, where clicks just don't register. Can't tell you how frustrating and time consuming it is to have to move a toolbar or window just to click.

Running a Macbook Pro 2021 with an apple USB-C to HDMI adaptor for an ASUS external monitor.

Checking daily to see if there's a software update.

I ended up downgrading my Mac mini to Sonoma because of this. Tried Sequoia 15.1, same issue. As opposed to the Macbook, on the mini I've no alternative to using the external display, and the display going off while I type vigorously isn't exactly my idea of fun.

tkatebini wrote:

Thanks for this! Quick question: are you only running one external monitor, and not multiple? I was able to run 2 before, and with the update, now only one works, and only one is detected by my mac. No issues with my DELL windows laptop.

Which mac? And how are the displays connected to your mac?

Did you update DisplayLink software, if you use that?

arcyarcy wrote:

I now remembered what I did to fix the issue last time this happened after a MacOS update:

Power your monitor off and turn it on again.

Just tried that on the MacBook (the mini is already back on 14 and will stay there until Apple fixes this.) Powered off the monitor, removed cable (HDMI) from both sides, waited 5 minutes, then reconnected the cable on both ends, powered on the monitor and ... in less than 1 hour it flickered twice, the first time 2 minutes after I powered it on! I guess the MacBook is on its way to 14, too...

Same issue here - I can't connect my HDMI cable to a ASUS screen. The connection keeps turning on and off - it is just a endless loop, like 3 seconds between. I tried updating DisplayLink to the newest, didn't work... The monitor works on my Windows laptop...

Similar issue with an M1 Max MBP with 2 external displays. One external falls asleep while I'm actively working and the other external does not. Both were functioning perfectly prior to upgrading to Sequoia 15.1.1.

I could be wrong, of course, and I hope to be, but barring any interference, this looks like a hardware problem.

Disconnect any peripherals, and see if there is any change.

You could also try installing an older OS in an external drive, and see if that makes any difference.

Ok, I found a fix for me. It's all backward.

I had a "higher quality" / faster HDMI cable that I have been using fine for the last year with lower OS versions. During the general troubleshooting with Apple support, I remember I still had the old "Amazon basics" cable that I had used prior to the better-quality cable.

I swapped the old cable, and now it works fine.

"Newer Cable"

https://www.amazon.com/gp/product/B0CJLC72MG/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

"Older Amazon Basic Cable"

https://www.amazon.com/gp/product/B083KX4F6K/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

An obvious culprit is that the old Amazon cable explicitly states the 60hz refresh rate while the newer cable lists higher refresh rates.

Now this has worked for a year so I think this suggests that there is something in the OS update that is forcing display connections closed if there is some sort of dissonance between the system refresh, connection, and display refresh.

At the end of the day I'd rather use my higher quality cable that has been good for the last year, but who knows when Apple will figure out this bug they introduced.

I have both a Viewsonic and a Samsung external and I see the issue in the Samsung. It’s pretty clearly a software quality issue unless a lot of displays from various manufacturers owned independently by users all over the country/world all failed coincidentally immediately following a software update from Apple.

This kind of stuff is why I never take X.0 releases from Apple anymore on any platform. The fact that this is happening in 15.1.1 just tells me the quality control has only gotten worse.

I have MacBook Pro 16" 2021 plus external monitor and iMac 2019 plus external monitor, both machines used for work in situations where a second monitor is essential. Both updated to Sequoia last week. No problems with the iMac external monitor but the MacBook external monitor keeps blacking out as described by others. It seems fine as long as I am working on something on that second screen but will disconnect itself when it hasn't been used for a few minutes. The only way to reconnect seems to be the classic unplug/replug and that doesn't always work.

I have no technical ability or available techie and it's really making life difficult and interrupting the workflow. When will Apple fix this?

Hi again,

Curious thing, with same computer, Macbook Pro 2018 Inter with T2Chip, the issue happens in one external TV, the one described in my previous post but it does NOT happens in another TV with same adapter, very weird.

This means that it does not happen to all monitors, it seems taht HDMI management has changed in some way that some vendors are not ready for?

Regards

I'm back to Sonoma on both the MacBook and the Mini. At least they seem to be supporting two previous OS versions, so I should be fine for a couple of years ... enough time for them to fix this issue?

Updated to 15.2 with fingers crossed and no luck still the same issue. External monitor comes on for a sec and then blank screen. No change with this update. Apple please fix this!! This is not just a little bug this is destroying a lot of peoples daily workflow. :(