No HDMI signal after update

I also called them few weeks ago, they told me that the problem was probably comming from my external monitor and that I should contact acer to ask if their planning to release a new driver to solve the issue.

I'm an computer scientist myself I knew it was total bull***t but I also knew the person that was speaking to me could not do any better. So I told her that I would not do that but if she could just let my issue open. I think that if we are many to have this issue and to complain about it, it might become a priority to them.

Haha,

I hesitated to buy the Belkin adaptator promoted on Apple's store thinking they might be evil enough to make other adaptators bug so you have to buy their own. But I would prefer to change the computer if it was true.

Yours definitely sounds like the worst case described here, most have been able to do the USB-C workaround. So they couldn’t even get a 1080p monitor working at the store? Pretty sad, sorry you’re in this mess.

This issue started right after install, I was able to connect to a 1080p tv via hdmi. I could then switch the cable to my 4K monitor and it worked as long as I did not shut down the computer (sleep was fine, it would wake up and continue to work). If I shut down I’d have to repeat the tv connection & then switch. Now nothing works. I think something is cooked regardless what their diagnostics say...

There is a fair bit of heat in some of these posts, and perhaps the is fair enough...

But frankly, I would have given Catalina 10.15 3 hours and if it still wasn't working with HDMI on my Mac mini, I would have gone back to Mojave - which is a fine product and works like a charm. Not sure I understand the "paperweight" comments and some of the hating going on here. Downgrade to Mojave and wait for Apple to sort it out. Why not????

Yesterday I switched back to Mojave on my Mac mini 2018 successfully with not HDMI issues any more !!!

First try was to go back in "Time Machine" but without success. Mojave running but still same HDMI issues.

Second try, I decided to a make a fresh Mojave installation using internet recovery ... this stoped of after downloading installation files with an error.

Last try, I created a Mojave USB installation stick. At the end of the complete installation procedure all HDMI issues are solved and my system is running as before Catalina.

Hope this will give you a temporarily solution until Apple solved this issue finally.

That's interesting as I was under the impression that the Catalina update also did a firmware update which prevented going back to Mojave. I wonder why the usb installation was successful and the other two attempts were not?

I'm still having problems with my mac mini but not as bad as others. Mine will only recognize the HDMI if I unplug my second monitor before boot up. Once its up and running I can then plug in my second monitor, usb c to vga, and everything works fine. If I leave the second monitor plugged in when I boot up it doesn't recognize the HDMI. So not the end of the world for me, I just have to keep unplugging and then plugging in the second monitor. Hopefully Apple will come up with a permanent fix soon.

Now that I've upgraded to Catalina 10.15.1, my problem has been partially fixed. If I restart the computer using the Restart command, HDMI is not recognized until I unplug the HDMI cable from the Mac Mini and then plug it back in. If I totally shut down and then power up using the power up button on the Mac mini, the HDMI is recognized from power up and both monitors work. Most of the time I can go into and out of Sleep mode with no problems, but once in awhile HDMI will not work when coming out of sleep mode.

“Most of the time I can go into and out of Sleep mode with no problems, but once in awhile HDMI will not work when coming out of sleep mode.”

I have that problem occasionally as well, though it’s been rare of late, I had it with Mojave too, but since 10.15.1, things have been pretty stable. I suspect there’s still something going on, I’m just one of the lucky ones who don’t have problems now.

I called Apple Support October 8th and then they ask for the logs. After I sent it to them, no one tried to contact me with this case.

I am amazed that Mac users around the world do not make a larger scandal. I see two options:

1) this problem is small - they will leave us with this mess

2) they don't want to do anything with it - it looks like a purposeful error.

Why I won't go back to previous OS? I will lost notepad and reminders synchronisation between Mac and iPhone.

Now it looks like I should buy new display. Preferably from apple.com ;)))

Since updating to 10.5.1 I am now getting random but frequent disconnecting mouse and keyboard issues, tried resetting bluetooth but no improvement, really getting ready to finally move away from Apple. Its just not working for me anymore. One issue after another.

I have a Mac mini 2018 hooked up to a 40 inch Samsung 4K TV / Monitor. Prior To Catalina, Mac mini would wake up and display video on the TV with no issue. As soon as I upgraded to Catalina, I have too hard reboot my Mac mini around 5 - 7 times to get into a forgot password mode where I then reset and can get into the MacMini. Also, my keyboard and mouse have been disconnecting randomly. Please Resolve.

I have had the same issue trying to connect a relatively old Sony Bravia TV through HDMI, was not detected by the MacBook Pro.

Found a fix though!

Ended up on this YouTube video: https://m.youtube.com/watch?v=8YwJ7xdSUAc

The guys goes to System Preferences -> Monitor and presses the alt key to force the detection of the TV and/or display the « Detect displays » button.

Hope this may help some of you!

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.

Same problem here. When I start my MacMini (2018) my Samsung 4K monitor says: "not optimum mode" and doesn't work. It's connected via HDMI and that happens since I updated to Catalina.

When I type in my password "blind" and to start Mac Mini, the monitor wakes up and works as it should. The problem is the booting process.

Since there were some advices here, I bought an "USB-C --> HDMI" cable. Now there's a slight improvement - SOMETIMES the monitor keeps starting just normal when I boot the mac. But a lot of times it stays as black. At least the error message from Samsung is gone now.

Apple, please fix this. :-/