Mac mini M4 Pro sporadically loses connection with external monitor

To all:

According to this topic: Mac mini running macOS Sequoia 15.5 experiencing brief 2 second blackouts, if you have the Zoom app installed removing it and all supporting files fixes the problem. I removed Zoom early yesterday and haven't had an outage since.

I've been getting the same issue with an M4 and LG 32" monitor. In fact there's another topic regarding this issue. From the info in the other topic it's not system, cable or monitor related. It appears it's a hardware issue, with M2, M4 and, I believe, M1 Minis experiencing the same problem.

All we can do is report the problem at the Apple Mac Minifeedback page: Mac Mini Feedback.  

As hcsitas has already suggested do not put the Mini to sleep. Just use the screen saver and have it go to black after a preset time:

Also if your local power lines are above ground or you experience frequent unplanned power outages I would not have the Mini automatically reboot after a power failure.

den.thed wrote:

Turn On "Prevent automatic sleeping when display is off"

Set "Turn display off when inactive" to 5 or 10 minutes

Leave the Mac Mini On and only allow the display(s) to turn Off

Do not manually Sleep from the Apple Drop Down menu

Shut Down the Mac when away for a day or more

As a test

Turn On "Prevent automatic sleeping when display is off"

Set "Turn display off when inactive" to 5 or 10 minutes

Leave the Mac Mini On and only allow the display(s) to turn Off

Do not manually Sleep from the Apple Drop Down menu

Shut Down the Mac when away for a day or more

Try the settings exactly as shown below (reboot after changing), should fix.

Also, do not manual Sleep, shut for long absences and let the display switch off on timer during normal use:

(or use Control-Command-Q to immediately lock your screen).

My problem seems be fixed after purchasing a new Anker USB C cable - no more gray screens since it was installed! I'll find our for sure after doing some more intensive video editing.

https://www.amazon.com/dp/B09YM3V7NX?ref=ppx_yo2ov_dt_b_fed_asin_title

Not sure how to stop this from happening, but while in display settings, holding down the Option key and selecting "Detect Displays" fixes this on the fly (so far).

Got the issue after updating to Sequoia 15.5 this morning on my Mac Mini M4 Pro (5/21/2025). Turns out the reason is the USB-C cable that came with the monitor is not a USB 4 (or Thunderbolt 4) or up. After I tried Thunderbolt 4 and 5 cables, the USB-C display connection back to normal. It was fine right before the update - might be some software requirement updated. Hope this helps!

Exact same issue with my M4 Mini and 2 identical Asus ProArt 27" 1440P displays. The HDMI connected display is fine, but the USB-C/Thunderbolt to DisplayPort one will not display with a system reboot. I must power cycle the monitor for it to display. I also bought the separate cable, since only a DP to DP cable was included in the box.

Extremely aggravating.

I exclusively use a Belkin UltraHD High-Speed 8K/4K HDMI 2.1 cable from my M4 Mac Mini Pro to an LG 32UN880-B 4K UltraFine display without any issues.

How long is that USB-C cable run to your LG display? Good luck with LG support.

Hi there. I have signal issues too from my Mac Mini M4 . I have an Asus TUF Gaming VG28UQL1A - 28’ LED IPS UltraHD 4K 144 Hz Monitor , and since I’ve buyed my Mac Mini M4 & PS5 PRO ,both were connected via HDMI 2.1 with their own cables on the two HDMI 2.1 monitor ports ( have 2 hdmi 2.1 , 2 hdmi 2.0 & 1 dp 1.4 ports in total) and no issues,meaning both devices when powered ON apart , signal automatically appears on monitor (even on PS5 PRO from PS button controller). Also I want to say that i never turn OFF my monitor(never gives me problems on anterior PC gaming setup). I’m thinking now , if could have something to do with the Blackout ( I live in Spain and past week we had a Blackout for a few hours & caught me playing on PS5 PRO ,but my Mac Mini was OFF). I’ve tried with another HDMI cable on on each one of those 4 HDMI ports ,but still no signal (cause my monitor is turning OFF when i turn OFF the PS5 and only way is to turn ON monitor and switch to Mac HDMI port connection,but turning ON also is turning ON my PS5 ,so just manually changing. Another option is worked : took off PS5 cable from monitor & let only the Mac connected,but not allways working. I even buyed an USB-C to DP 1.4 cable,but no signal . I’ll try to see if i have to do some change on Mac to getting work.