2018 Mac Mini - monitor problems

On the phone last night with Apple Support. The person I spoke with had a hardware background and he kept pointing in the direction of a wattage issue. He checked the spec's of the monitors I was using and thought it was too much wattage causing one monitor to go to sleep when waking, (HP 22). To test he had me reduce both monitors to 1080p, and they both functioned perfectly waking/restarting. But I didn't buy a 4K monitor to view in 1080p. He also kept saying that the mini is spec'd to give 4K through HDMI to HDMI. Later I checked what Apple was saying, and indeed one monitor should carry 4K at 60hz. So I checked with Samsung and downloaded the manual that did not come with the monitor. And had my Duh! moment. Only through HDMI 2 does the monitor give 4K at 60hz. Everything works perfectly now. If Samsung spent $.25 and added this information with the product I never would have had an issue. Of course I should have checked earlier too. I was only running two monitors because the Samsung would not wake during a restart or cold start using USB C to Displayport. I now have one monitor running 3840x2160 @60hz.

I have the same problem on my macmini 2018 with Mojave 10.14.5 using HDMI connection.

Today I tested the followings;

Test 10.14.5 using USB-C->HDMI converter Result: worked OK

Test 10.14.4 (newly installed) using HDMI cable Result: worked OK

Test 10.14.5 (updated from above 10.14.4) using HDMI cable Result: this problem re-created!

Test 10.14.6 beta1 using HDMI cable Result: OK

Test using 10.15 beta using HDMI cable Result:OK

From my tests, this problem seems to occure only on Mojave 10.14.5 with HDMI cable connection!

At moment, I use Mojave 10.14.5 using USB-C->HDMI converter and wait for nets Mojave update to 10.14.6.

I have the fix!!!

Install Mojave Version 10.14.6 Beta!

After returning one 2018 Man Mini, I ordered a second one and had the exact same problems. I was preparing to return the second unit, when out of desperation I tried the Mojave 10.14.6 Beta. I now can restart my Mac Mini endlessly with never a problem. Try it, you'll like it!!!

Now that I have joined the beta club and installed the new OS Catalina, I have not had a problem with my monitor not connecting on reboot and as well on cold start. Updating to Catalina has fixed all monitor problems for me. This after me having to return my 2018 Mac Mini and getting another only to have same problem. Monitor loosing signal. A lot!!!!!!!!!

I hope this will help others if they want to get beta Catalina and upgrade. Everything has run well for me on Catalina. No bugs to report, other than 32 bit apps are no longer supported. I can live with that now that my monitor connects how it should. Thanks for your time.

I have now been on Mac Catalina os for a month now and my monitor that was loosing connection on a regular basis has not failed once in a month of use. I can now say for sure problem solved. As with friend who had dual monitor trouble, after update no more worries. Catalina beta was my answer. Hope this helps others.

I have a possible fix for some people. I have a 2018 Mini with a Dell 4k monitor, and a Dell U2415 1920x1200 monitor. They are both connected via USB-C to mini DP in the monitors. I did one time have an issue with the 4k not turning on, but that was a rare event. But almost always when the computer went to sleep, the older U2415 display wouldn't come back online. Restarting the computer would get both monitors back, so I was restarting several times a day.

After months of agony, I found this option in the U2415 menu. By default it was disabled, but since I've changed it I haven't had any issues with losing that display.

Display -> DP 1.2 -> Enable

SEND IT BACK TODAY. DO NOT DELAY.

GET A REPLACEMENT iMAC ($2500) or DELL / LENOVO HP / ASUS et al i9 ($1500, similar specs).

THERE IS NO FIX FROM APPLE, and it would seem that NO FIX IS FORTHCOMING.

DOES NOT WORK RELIABLY with 10.14.6 or 10.15.x

SORRY, the cost / performance ratio of the i7 MINI is the best from Apple, but the device simply does not work reliably. You can try 10 to 20 cables / adapters / different brand monitors (I have) and find a semi-stable solution, but then it gets unstable with the next OS update. You WILL WASTE $100s on cables; $500s on moniters; $1000s of your own time and grief, and still wonder, each morning, as to whether or not the machine will start up, and whether it is safe to shut down the computer and try a cold restart after a week. Anything can happen on restart, from hours of grief and black screens with attendant cable switching, screen switching, etc. , to full proper restart. It is mystery.

After 18,000 posts, APPLE has not fixed the problem. The MINI i7 JUST DOES NOT WORK reliably with multiple monitors, external thunderbolt drives, file vaults. The underlying issues are thermal, firmware, software, internal startup sequence, powering of the various busses, and/or sending out passwords to external encrypted drives, etc. All these are in play.

APPLE has not fixed it after 10 months of grief from 1000s of customers (maybe more, but not everyone posts).

BITE the bullet.. get rid of the MINI (get a full refund from Apple), and move onto something else that is reliable. If you have to, CRY when you are at the Genius Bar... maybe they will take sympathy and refund your money.

Do not get another MINI.... all minis seem to be afflicted (I am on my second 2018 i7 mini - both have the same issues).

If not, you will CRY for months or years with your afflicted MINI.

I was running into this exact same issue. I have a 2018 Mac Mini (512 GB SSD, 16GB RAM, Core i5 processor). Have two HP 27es monitors. One connected directly to HDMI and the other connected via USB-C using a USB-C to HDMI dedicated cable - not an adapter.

I reset NVRAM per Apple Technical Support but that fix only lasted a few hours. I rebuilt my entire Mac thinking maybe something in the OS became corrupt. No luck.

The short term fix for me was simple - used a USB-C port for my second monitor which was working fine. Per a senior advisor at Apple Support, they believe the issue was software and not hardware and that Apple was aware of the problem.

I ran the latest update to 10.15 yesterday and decided just to try and reconnecting one monitor directly to the HDMI port on the Mac Mini. Worked and has been working since. System has been going in and out of hibernation and still getting both monitors back.

I do have a case number with Apple should the issue arise again. I am going to press for an RMA of the device if it happens again.

Hope this helps.

Apple replaced my Mac Mini at the weekend and while I was incredibly skeptical, its been running for a few days with no issues. I've got the LG monitor connected usb-c to usb-c and its been 100% reliable when waking from sleep or powered-off. I'm genuinely surprised...

I've got Filevault enabled and have not adjusted any boot settings, display settings or installed any 3rd party software related to the display.

I've not tried HDMI to HDMI yet - will give that a go tomorrow. I was convinced this was a software issue, but maybe its not as simple as that?

I have a 2018 mac mini i7 which refused to connect to a single monitor over usb-c or hdmi on wake-up, re-start or boot-up. The machines been back to Apple for a new 'logic board'. This didn't fix the problem.

The good news is that following the advice below, which I read on this thread somewhere, seems to have fixed the problem / improved the situation:

• Go to Apple > About This Mac > Displays
• Click 'Displays Preferences...'
• Press 'option' key. This makes a 'Detect Displays' button appear bottom right of screen.
• Press 'Detect Displays' twice.

Thanks to the original author of this advice. Sorry, can't find the post again to thank you directly.

The other useful advice was: press option and command keys (not together) during wake-up/restart if screen appears dark.

I have a call booked with Apple tomorrow morning re this problem. I'll keep testing to see if this improvement is permanent or just temporary.

Apparently, 10.15.3 has been released today and I was told by Apple support that it contains a fix for HDMI which is now confirmed by them to be an issue. I've been working with Apple Support since October about this issue.

Report back here your experience after installing the update. I'm just installing it now.

Few days back I updated to OS 10.15.3 and changed from usb-c/DisplayPort cable to a HDMI cable. This seems to have fixed the wake-up screen problem on my Mac Mini. Fingers crossed it remains fixed over future OS updates.

The newest public beta of 10.15.4 just released today solved the problem for me. I can connect HDMI to HDMI or USB-C to DisplayPort and I get the Apple logo on boot. I can even enable the FileVault login.

At first I thought it didn’t work but a power down and back up and it’s worked fine since then. I’m using a Samsung 4K 28-inch.

After more than a year, 10.15.4 fixed everything for me. My Samsung 4K monitor works on boot when connected USB-C to DisplayPort or HDMI to HDMI.

I also get the Apple logo and login with FileVault.

I’m not sure what’s different about everyone’s setup.

This appears to be fixed in the current public beta of Mojave.

You can get it at http://beta.apple.com