M1 Mac Mini, Displays wont turn on after wake from sleep

Well, if you really disabled sleep, it won't need waking. So that would point to an issue with your LG (check settings). If you didn't disable sleep, do it by going to System Preferences > Energy Saver > Prevent computer from sleeping. Good luck.

The box I have checked (since yesterday) in Energy Saver says "Prevent computer from sleeping automatically when the display is off." That's the only box that has to do with sleep that I can find. I assumed "sleeping" had to do with the computer and not the display, meaning certain systems in the computer would not "sleep."

Also, even if I use a hot corner to enable Lock Screen when I step away from the computer for 10 minutes or so, the Lock Screen will eventually "sleep" the monitor - even though I have "Turn display off after" set to 3 hours. So the problem persists anytime you just want to lock your screen to step away from your desk.

However the problem I have persists even on startup of the new computer. For example, last night I shut down the computer completely just to leave it off and not worry about the problem overnight. This morning when I powered up, the monitor would not wake up or I assume the Mac mini did not recognize the monitor. I unplugged the Thunderbolt cable several times but it still didn't work. Finally I did another hard reboot (pressed the power button) and it finally came on (with a weird green screen on power up).

So I don't think the problem is just a matter of the "sleep" setting in Energy Saver menu.

Well in that case, it's definitely LG. Too bad because their support socks. Try fiddling with the monitor settings, might get lucky...otherwise replace or live with it, I wouldn't count on a "fix" from Apple (if you go the replace way, avoid wide screens).

What about my post leads you to believe it's definitively the LG monitor? I have used this monitor with no issues with my 2019 16" MacBook Pro both with Catalina and for the past month with Big Sur. There are no energy settings enabled on the monitor. Seems to only be an issue since adding the Mac mini last night. With all of the posts mentioning similar display problems it seems odd that simply because I have the sleep button checked it would definitely be my LG monitor.

EDIT: Just swapped over to my MBP and went through all of the Lock Screen/sleep etc procedures and every single time my monitor woke up with a spacebar tap - seems to be a problem with the Mini, which unfortunately I think will be going back.

I had the same problem with multiple monitors on my 2018 Intel Mac mini (never solved to this day), but, wait, my 2020 M1 Mac mini does *not* have this issue (monitor connected via USB-C to VGA as were the Intels). Go figure!

Yes, some people say that they solved the problem by connecting the Mac mini to VGA. The problem seems to appear when the connection is HDMI or DP. I can only connect to those ports, so I’m expecting Apple to solve it.

Similarly, I have had my M1 Mac mini for 3 days now. I have one Acer monitor connected with a HDMI cable, and one Samsung UHD monitor connected with a Displayport-to-USB-C cable. I wake and sleep the computer 3 or 4 times a day, when I walk away for extended times. This afternoon I woke the computer to one monitor (USB-C) only, the other was black screen only. No open apps were visible on the one screen. Only a reboot of the Mac mini fixed it. And suddenly open apps were on both screens once again, just as a left it a few hours ago. I did not unplug monitors, I just rebooted.

Yes. The display configuration changes every time, sometimes randomly. Even when I keep the computer always running (never sleep) and turn off the monitors manually (press the On/Off buttons). When I turn the monitors back on, the arrangement and the scales are wrong. It looks like the Mac mini was not properly tested. I guess these issues will be solved with a system update, but we have to put some pressure on Apple to do it. Some people are already returning their machines, but I need it so I can't do that.

It would appear that this is a monitor waking issue and not a computer waking issue. So right now, I just set "Turn display off after" to never which is certainly far from ideal. At least I have until January 8th to return it! Hopefully, the next OS update will correct the issue.

It would be really nice if Apple would have a known issues list or something but I have to say other than this monitor issue, possibly an issue with getting AirPods to reliably connect, and a periodic crash issue, I would have to say my M1 Mac mini has worked remarkably well. I expected more issues with a new processor along with the normal bugs in a next version OS.

You haven’t posted details so unable to comment further. You can anyway always manually switch monitor off.

Looks like an M1 issue assuming your monitor isn’t dongled, dualed or otherwise setup differently. Good luck.

The issue is the same, I think, as the original on this thread. One monitor hooked up USB-C to DisplayPort and one by the HDMI port on the M1 mini. Works fine at first but then eventually the HDMI monitor will not wake back up. I had already set it to not sleep when the monitors turn off. When it happens, it displays what should be on the monitor that is on for a few seconds and then switches to what should be on the HDMI monitor for a few seconds over and over. Unplugging the HDMI cable and reconnecting it fixes the issue until it does it again. If it is the same problem, I was just pointing out that preventing the computer from sleeping does not fix it - you have to prevent to monitors from turning off.

I am confused. The monitor that is connected using the USB-C to DisplayPort cable comes on every time. It is the one connected to the built in HDMI port that seems to be having issues. Also, it works until it doesn't and then I have to unplug and reconnect the HDMI cable or restart the computer to get it to work again. I searched for problems with dongles being used to convert to DisplayPort and I found some that talked about the monitor with the dongle not working but I could not find where the USB-C to DisplayPort cable (dongle) works but causes the built in HDMI port to not work.

I did find this: https://forums.macrumors.com/threads/m1-mac-mini-not-waking-display-after-sleep.2270758/. They are reporting happening when only using one monitor connected to HDMI. I am not sure if it is okay to post links on this site. Sorry if it isn't. I suppose I will just contact support - at this point it would have been faster.

Well, it’s monitor and dongle dependent. My single HDMI Dell has worked without a hitch from day 1 late 2018. I should add that I’m on a mission to rid the world of dongles, DVI-capable monitors, eGPUs and crowded USB hubs, something I suspect Apple is too. IMO, anyone using these are powerless users who like more to fidget endlessly with cables, backups, restores, recoveries and the like than getting on with real work.

I don’t think Apple Support will help you, but you’ll definitely get more sympathy than my post here. Nonetheless, I’ll let you go through the hoops with them. If you’d rather not, I recommend you ditch the dual monitor config and stick to HDMI until dongle-proof USB 4 monitors start rolling out, which should happen late 2021. Good luck!

It’s very simple: disable sleep on the mini, use one HDMI monitor and wait it out for the second one until newer monitors with dongle-proof USB 4s hit the market (or buy an expensive TB3 monitor). Enjoy...