No HDMI signal after update

this is what gets me , apple is aware of the problem so why don’t they pass the info to their tech support people . instead of wasting time why not just tell people calling in about the work around until apple fixes the problem. i no problem using the usb c adapter and only after giving up on tech support after two hours and two days did i by chance pick up a adapter to try out.

To be clear the only solution is a usb c to hdmi adaptor. I tried everything multiple times and actually did get the hdmi to work after resetting the Mac but only once for long term fix you need to use the usb c - hdmi adapter. It is software so it is not intentional and bugs happen. I bet we get a soft ware fix soon:)

As others have mentioned, the only solution today is a USB-c to HDMI to restore 60Hz 4K.

A workaround (at least for me) was to manually cycle through the inputs on my monitor’s physical controls. This allowed the HDMI-HDMI Connection to work correctly, without any image distortion.

After Catalina update on my 2018 Mac Mini, the HDMI signal to my Sony 4K bravia failed (no issues before the update). After reading through this post I decided to get Apple Support involved (misery loves company). After 2 hours of attempting everything shy of connecting another monitor (which I don't have), I requested a visit to my local Apple Service Center. Predictably, they could not duplicate the issue using a USB-C-to-DVI cable. I informed them that the issue was with HDMI video, to which they had to buy a cable to troubleshoot with - UGH! They still didn't fully understand the HDMI configuration that many on this forum are using - HDMI-to-HDMI 4K monitors (UHD TVs or otherwise) and still could not duplicate the issue. So, I bit the bullet and bought Apple's $69 USB-C Digital AV Multiport Adapter. Connected BOTH HDMI and USB-C/HDMI from the mini to separate HDMI inputs on the TV. When powered on with HDMI source selected, no signal. Changed source to USB-C/HDMI - WOW! got video. Now the test: switched BACK to HDMI-direct - signal remained! However, when cycling TV power, I have to repeat the source-switching dance to regain the 4K 60hz HDMI signal (research indicated the Multiport Adapter output is only 30hz). I have reported my findings back to Apple Support and hope this helps them and many of you.

I'm expecting a cloud to open and sunrays to shine through ... or a lightning bolt will hit me ... but ...

Since installing the macOS 10.15.1 update on my system this morning, I can now run my monitor with only the HDMI cable and port AND I can shut the power off! I've done it several times, and not only does it work, but it gives me back the highest 3840 x 2160 resolution I wasn't getting from the USB-C to HDMI Adapter (best was 3200 x 1800 with it).

Please someone else try this and let me know it really works as I may be dreaming ...

Update: The last time I not only did a "Shut Down", but I pulled the power cable on my mini and waited about a minute. Plugged it back in and it started right up -- my Mac mini 2018 and Toshiba UHD TV/Monitor now powers up and displays 4K via only the HDMI port and cable.

I had the same good luck with the 10.15.1 update

after updated rebooted (power down ) and the after everything settled down . Power down and hook directly to the HDMI port and powered up.

display came up right away 4K hdr 60 hz to my lg 4K monitor via HDMI .

seems 10.15.1 addresses the issue

After updating to Catalina, my mac mini no longer recognizes HDMI signal, and my monitor is blank. I tried switching monitors and HDMI cables, and I intermittently get a signal, but it remains a problem. I have to use USB-C to HDMI adapter and then turn on/off my mac by holding the power button for 2-3 times before I can see the screen and then restart my mac. Then I get a signal, but it's a 15 minute rodeo every morning. Apple, please fix this problem ASAP.

The problem so far

The problems around this thread seem to revolve around 2018 Mac Minis with 4K monitors not sending HDMI output / sending bad video output while starting up. And for some reason, the BIOS (or whatever is called) sends a resolution in the first screen that is not quite supported by 4K monitors or when detects a 4k monitor somehow manages to screw up the output on them, unless they are limited only to 30hz or similar.

Fixes that have failed

USB-C to DP: I have tried a USB-C to DisplayPort cable and it doesn't fix anything, but in my case the issue wasn't the HDMI port itself, but the incompatible resolution it sends, so the only difference on my monitor is that when in HDMI I get a message about incompatible mode and while in DP I just get an acknowledgement of receiving signal but no image.

Resetting NVRAM: I have also tried resetting the NVRAM, and kinda works one time, but only for that specific boot right after the reset, and sometimes with pink colors or similar bad output issues. .. and the next boot I will get exactly the same issues of not being able to get an output that my monitor can display, so it is not a sustainable fix (can't reset the NVRAM in every boot! and in the era of bluetooth, I need to dust off my USB keyboard to do so). Also the screen is on 4k without any scaling so using the mouse is annoying in that screen as well.

10.5.1: With 10.5.1 the issue remains the same... and as I have been reading that downgrading to 10.4 will not fix anything since something changed at a more fundamental level (BIOS?). So we cannot go really back to normal.

C'mon Apple take action!

Please, Apple, do your due dilligence and solve this issue. We need reliable setups. A recent Mac Mini with a Samsung 4k monitor (and according to other posts, also happened with Sony and LG TV/monitors) is not an extraordinary setup. And clearly we are many with the same issue, who are forced to use a spare monitor, or to blindly type their password. I don't think that anybody would spend >1k dollars to have such an unreliable fix.

Is there more to it?

Also, is it possible that there is a batch of mac minis with some hardware issue that is leading to this outcome?

No... There is NO fix as of yet from Apple.

I just got off the phone with the Apple Engineering team, and they are still working on a fix, but have nothing to show for it at the moment. 10.15.1 has nothing in it to fix this, and if people are seeing changes in behavior it is most likely down to re-boots, and not cold-boots.

This is a strange matter indeed. Should have been more "read me first" with this upgrade IMO

My Applecare tech explained the NVRAM reset was my likely solution and it worked for my 2018 MBP.

Catalina led to other issues with the Mac Pro work station, such as the WACOM tablet not being visible and "drunk", and an old BARCO graphics monitor not loading. The former I solved with a driver update from WACOM, the later "fixed itself". Having the latest drivers, as possible, certain key.

SMC

He also noted had the NVRAM not fixed it we would thenreview System Management Controller (SMC) as certain low level functions may be tweaked by the upgrade - Different steps depending on the model.

No longer supporting 32 bit

The tech's comments was that this problem was in the NVRAM settings - but also pointed to the new OS deleted support for 32 bit altogether - which may, he surmised, cause issues with monitors, if their drivers do not support that change. He said this was a notable distinct "1/0" with Catalina

I resolved the video issues by using a USB-C to HDMI cable, resolving the Bluetooth issues may be interference from the WIFI, many have fixed this by moving WIFI to 5GHz to create less interference than having both on 2.4GHz.

I would call Apple Support, when they answer ask immediately for a "senior advisor". Then tell them that you updated to 10.15.1 and the issue you are having. Tell them that you are aware that the Adapter FW is NOT 2.15 which it should be, and how do they propose to rectify the issue. Unfortunately it has become abundantly clear that you need to take control with these people. Most of them seem to act like the "know all", but if you actually do know what you're talking about, it doesn't seem that you need much more than a basic knowledge to be on par or beyond their level of knowledge, they will quickly admit that you are more knowledgeable about the issue than they are, and usually offer to pass you on to a supervisor or research the issue and get back to you. Whether they actually will get back to you is questionable as well... It has become frustratingly clear that they have a script and check list they work off and no practical knowledge or experience ant the basic support level. It's questionable how much "knowledge and practical experience" the average "senior support" people have.

Same here went back to Mojave and hdmi port was still dead . Installed a usb c to hdmi and reloaded Catalina

Just have the bulletin from someone else, text below.

Apple Technical Service Bulletin

This document provides additional instructions for operating the Mac Mini (Late 2018)

macOS Catalina 10.15

Mac Mini (Late 2018) users should refrain from upgrading to macOS Catalina 10.15.

https://www.apple.com/macos/catalina/

Information about products not manufactured by Apple, or independent websites not

controlled or tested by Apple, is provided without recommendation or endorsement. Apple

assumes no responsibility with regard to the selection, performance, or use of third-party

websites or products. Apple makes no representations regarding third-party website

accuracy or reliability. Risks are inherent in the use of the Internet. Contact the vendor for

additional information. Other company and product names may be trademarks of their

respective owners.

Published Date: October 12, 2019

An odd development, yesterday I could not get my HDMI monitor to work at all. Unplugging, reboot, etc., none of the usual tricks worked. then I decided to try my monitor on another machine like I’ve done countless times.

I plugged my hdmi cable into an old MacBook Pro, the monitor worked as usual. But then I plugged it into the mini and it came on.

no idea why, but plugging my monitor into another machine, then back in the mini fixed it this time. Doesn’t make much sense, but maybe it will help someone else out until Apple fixes this.