External Monitor not receiving signal/intermittently receiving signal from mac

I've had this problem from Day 1 with a Mac Mini M1 and 2 external monitors - I started at 11.1 and 6 months later I'm now at 11.5.1 and there is no change. They did fix the bluetooth disconnect problem with 11.4 though. I've been through to third line at Apple. They promised a call back over the weekend but didn't bother to call despite booking it in with me. It's a major problem as the windows all move towards the primary monitor on every sleep. Sometimes they get there. Sometimes they end up off the screen. Workflow is considerably worse than on my MBP2012. 11.5 has also broken spotlight so I can't find emails now (I'll start a different thread). Honestly I'm considering a Windows 11 machine. This is the worst functionality I've had in over 30 years.

Hi contextCue,

We see you're having issues with your external monitor for the Mac, and we can help out.

You've tried some great steps already. Be sure to also apply the latest macOS version (currently macOS 11.5.1), to ensure all available fixes and improvements are installed: Update macOS on Mac

Then, check out any applicable suggestions from here, including trying a different adapter/hub, if you're using one: If your external display isn't detected or appears blurry on your Mac

If you continue to experience issues, you may wish to follow up directly with Apple Support for further investigation: Get Support

Take care.

Thanks Luis but I disagree. This is the same problem. I perhaps didn't explain too well. The secondary monitor frequently doesn't wake up. The primary monitor sometimes doesn't wake up either. Like @contextCue I've tried all the hardware changes. I've even bought an external dock with a display port to see if that would help (it didn't). When neither monitor will come back on you have no option but to take the machine down with a hard reset. If the primary monitor comes up then often (but not always) unplugging the secondary monitor (HDMI into a genuine Apple multi-adaptor) brings up the second monitor. Whether or not the second monitor comes up or not all the windows will have moved as I mentioned above as though the monitor was no longer present. This happens multiple times a day. As I also said above, sometimes the windows have to be found with an F3 as they are off the visible screen. While I admire your faith in Etrecheck for this , I'm pretty sure this is a hardware / firmware problem that has been present from when I plugged the machine in on Day 1 - the monitors are brand new too LG C32R50 . I have a second M1 Mini using different monitors but displaying (or not) the same issues too. I'm happy for you that you have no problems. I have a significant investment which is unfit for purpose.

Yours seems to be a different issue. I suggest you start a new thread, and give all the relevant details.

Many people apparently use the Mini M1 with two displays, and I don't recall seeing this mentioned (though it may have escaped me).

I recommend you run Etrecheck and post its report here using the "additional text" button.

Maybe it is a firmware issue, maybe not.

In another thread, someone with issues with displays on a similar mac reported that changing to a different dock helped.

Only you have access to your mac and can do steps to troubleshoot. If it is a firmware or OS issue, then it is likely to fixed at some point; but if the matter is caused by some third party kernel extension then you will end up in frustration every time a new update comes along and doesn't fix the problem. It is up to you to keep waiting or to do more testing.

The fact that it happens in more than one mac is something that very understandably may convince one that it is a systemic problem; but more often than not similar macs owned by the same person or organization have similar problems - because the installation is also similar or identical. If you had used, say "cleanmymac" on all your macs (just as an example) and all showed problems, it would not mean there was a firmware bug.

Understood - I've removed the Presonus kernel extension as it's not critical on this machine but on the reboot after this removal the secondary screen (HDMI in Apple Multi-adapter) had to be plugged and unplugged to be coaxed into life which doesn't bode well. I'll monitor the situation and compare with the machine with it still in. Both are Mac Mini M1 running 11.5.1

Another couple of days and there is no real difference - it's still Russian Roulette every time the secondary monitor sleeps whether it comes back on on resume or not. Primary Monitor has been OK although I couldn't get into the machine this morning as it wouldn't take the password - I had to take the machine down with a. hard power switch hold. This reminds me on startup, it's a full minute after 'dung' to seeing anything on the primary screen - just in case that chimes with anyone.

Just an update - I've had Big Sur 11.5.2 running since the weekend and have only had one failure of the secondary monitor to come up in 4 days. This is a major change from the Russian Roulette every time you walk away from the keyboard. I've noticed that the windows move around more predictably and stay accessible. Chrome always parks itself half way on each monitor, everything else heads to the HDMI direct main screen multiple times a day. So, an improvement from the update with no name. Keep going and with leaving the windows where they I left them though.

A further update - since 11.5.2 I've only had one incidence of secondary monitor not waking up. The open windows still migrate towards the primary monitor and some actually make it. None have manifested off-screen requiring fishing trips to access them. I'll take this as an improvement.

On the downside I've had 3 magic mouse disconnections and two keyboard disconnections which is the first time for quite a while. Not nearly as frequent as they used to be in the early days of Big Sur but enough to be disconcerting. They were both cleared by the "turning it on and off again" process.

I'm on Big Sur 11.5.2 and it has messed up the external connections from my Airbook Pro. It seems to support either an external monitor on the thunderbird port or multiple devices on the usb hub - not both simultaneously. So my advice if you are having problems is to (a) disconnect external hubs or docking stations (b) hope they fix the bug soon.

That's an interesting thought @MartinChuzzlewit - The M1 Mac Mini has been much more stable since 11.5.2 for me - I have a Caldigit TS3 plugged in because er... I need the ports and the Machine doesn't offer them. Way back when I first got the machine, this was the only way I could actually get the two monitors to work at all. One in the HDMI of the Mac Mini and one in the Thunderbolt port of the dock with a multi-adapter. I tried a native HP Display port monitor instead but not a glimmer - Maybe I'll have another go.. I'm also having more luck with Sidecar and my iPAD these days. Maybe 80% first time connection.