Display does not recognize after monitor goes to the standby

Macs can not recognize ANY display that is off or sleeping.

The Mac does not rely on windows-like side-loaded "Drivers" which are actually packages of resolutions and settings for a specific display. Instead, it goes straight to the immutable source -- it asks the display itself.

To get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, the display will not be shown as present, and no data will be sent to the display. "No signal detected" is generated by the DISPLAY, not by the Mac.

This query is only sent at certain times:

• at startup

• at wake from sleep — so momentarily sleeping and waking your Mac may work

• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go

• hold the Option key while you click on the (Detect Display) button that will appear in Displays preferences (from another display)

Your display must be responsive enough to answer that query, or it stays dark.

My recommendation would be to disable that feature in the display (using "on-screen display" settings) and use the Mac's ability to blank the screen when not needed.

Update:

I tried a new thunderbolt cable (Sounix USB 4 kabel - 40Gbps - 100W) and now the monitor does wake up again.

Looks like Apple changed something what causes certain other cables not to work anymore.

After updating to 15.1 I can (with limited testing) confirm that it is now once again working and it indeed WAS a MacOS issue.

The length and type of the cable should not matter, if the monitor is waking up perfectly fine for long periods (over a year without an issue) and then stops to work normally after an update.

If you are running a 4K or higher resolution display, its data rate required is very near the limits of switching speeds for the type of digital logic used to connect to displays. If there is too much cable length, the attenuation (slight decay) of the signals can cause data errors. When the Mac sees data errors, it shuts off the display.

That is why using appropriately-short data cables for each protocol solves so may user issues.

This is entirely misleading. Firstly, there's no "querying" of a display.. if the display has power, is set to the correct input and is connected to the Mac.. that's ALL that's to it. The Mac generates a signal and sends that signal to the display.

Yes, certainly there's some metadata (if we keep it simple and call it that) which the display returns to define maximum resolution and whether it's HDR compatible etc.. but at no point does the screen turn around and say "Hey, I'm awake, send me a signal" just because it's in sleep mode unless it's just powering on for the first time.

The reason the display is in sleep mode is because the Mac stopped sending the signal, due to various reasons. Disconnection or the Mac went to sleep. When the Mac wakes up, the Mac sends the wake signal to the display, as the signal is sent from the Mac via the cable to the display. It's been this way forever and nothing in display technology changes this basic functionality for decades.

The issue that the original poster is highlighting here, is one that has been present in various macOS version since the release of Apple Silicon Macs. I personally invested in 3 brand new displays after having this issue with some older Dell 2412M displays, all functioned perfectly on a Mac Pro but started randomly not waking from sleep when moving to my Mac Mini M2 Pro.

The new screens I purchased were all released in 2023, all identical 1440p SE2723DS and fully compatible with the latest standards, as well as high quality cables. Immediately after buying those 3 displays, I continued to have issues under macOS Ventura. I even posted about it on the MacOS reddit community, as pictured below.

When we went to Sonoma, the issue was resolved across ALL displays, including the older 2412M displays. Unfortunately, as of 15.1, this issue has re-emerged, with at least 1 display randomly not waking from sleep.

All logical people here would determine that if the hardware hasn't changed, if the setup hasn't changed but the only thing to have changed is the software, then the most likely issue here is with the software, not the hardware.

Discussions about cable lengths, quality of cables, sleep and power states are irrelevant, if everything that wasn't working before, was fixed via software updates and then subsequently broken again by a later software update.

Displays are not rocket science. At a basic level they are "Have signal? = Display signal".. If macOS forgets a screen is connected because it forgets to send a signal to the USB-C connection where the display was connected just 15 minutes ago, then that's entirely a macOS problem.

Frankly, I'm very frustrated that this issue has re-emerged. I have to unplug and plug the display back into the back of the Mac Mini in order to regain signal. I also seem to have noticed that USB SSD drives are randomly ejecting at times and will refuse to re-mount using the same USB-A port until switched to another port.. again, since 15.1.

Sorry if I came across a bit strong, but people will read your post and take it at face value based on your various contributions to this community.

There's no excuse for something to stop working which has worked fine before.. unless something is broken. In this case, it's not the display or cables.

the "punchline" on that thread you referenced is to upgrade your CABLE to a cable appropriate for the requirements of your high-end display.

Is that your solution as well?

if not certain, post your make&model display, or a link to its specs, for analysis.

YOU are the one who provided the link to another thread. Yes, it could be a less than adequate cable in contributing to the problem.

But if the display does not appear as a listed display in Settings/Prefs > Displays. you ALSO must turn off the display sleep feature inside the display, which is what I first said.

Substituting a Different cable is only a hedge against a BROKEN cable. High-end displays require MORE.

The benQ PD3205U appears to be a 4K display. Because of the very high data rates requires to run a 4K display the exact cables required are different from 'ordinary' cables.

for USB-C cables, the cable must be one meter or shorter. The cables sold as USB-4 are no exception. If longer than one meter, the signals will deteriorate and display will go dark (or never light up).

for HDMI cables, certified cables labelled PREMUM or ULTRA must be used.

For DisplayPort cable/adapters, the lead-in portion of the cable Before the converter electronics must be shorter than one meter, AND the remainder of the cable AFTER the electronics must be shorter than one meter. If the electronic are in one fat end, the entire cable must be under one meter.

EmadSmart wrote:

I bought the cable with a high price. But my problem doesn't fix, still the BenQ monitor does not awake after two minutes of macbook turns off. What should I do? Should I wait for a bugfix from apple?

No. Adjust the settings in-side the DISPLAY to NOT go to sleep.

<< This is entirely misleading. Firstly, there's no "querying" of a display.. if the display has power, is set to the correct input and is connected to the Mac.. that's ALL that's to it. The Mac generates a signal and sends that signal to the display. >.

Your statement as written is not correct. what resolution? what timing? are very important items that must be known.

The Mac does not rely on windows-like side-loaded "Drivers" which are actually packages of resolutions and settings for a specific display. Instead, it goes straight to the immutable source -- it asks the display itself.

To get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, the display will not be shown as present, and no data will be sent to the display. "No signal detected" is generated by the DISPLAY, not by the Mac.

This query is only sent at certain times:

• at startup

• at wake from sleep — so momentarily sleeping and waking your Mac may work

• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go

• hold the Option key while you click on the (Detect Display) button that will appear in Displays preferences (from another display)

I have the same issue! Before MacOS sequoia my BenQ PD3205UA woke up by pressing a random key on my keyboard, after the update to Sequoia the monitor doesn't wake up anymore. I have to turn the monitor off and on again the get the display working.

The problem is only with my BenQ monitor, my LG monitor does wake-up with MacOs Sequoia.

I cannot disagree any harder with you.

Periodically, I have the very same issue. 2 external monitors connected to a M1 pro macbook - one with HDMI other with USB-C. The HDMI wakes up every time without a problem. USB C doesn't wake up until replugging it.

This only happenes in the periods after an update, and a newer update usually fixed it. Sequoia being the lastest one that broke it..

Testing currently to see if 15.1 fixes it again.

<< when the monitor is not shown in the list, when I click detect displays, nothing is detected. >>

that demonstrates that the display does not respond to the Mac query when internally sleeping.

Some displays are set internally to 'favor' one computer interface over others.

It may be that your display favors HDMI, and listens to HDMI query form the Mac while asleep, but does not listen to all interfaces unless the display is not doing its internal sleeping.

When the display does not show up in response to (Detect Displays) button, it is not responding to queries form the Mac.