No HDMI signal after update

Note that this issue occurs with 3rd party hardware as well. My MBP uses a OWC USBc Dock when it is at my desk. Catalina update (including the .1 release overnight) has resulted in the HDMI-port of the dock only holding a "synch" with an external monitor for about 10 seconds, and then blue screening.

Plugging the same screen in via a USBC-HDMI adapter and it works fine.

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????

I am pretty sure this is an issue with HDMI and Catalina. When using my two external monitors with USB-C to HDMI leads it takes ages for them to be recognised (30 mins or more). I switched them for USB-C to DVI cables and the monitors are recognised instantly.

SOLUTION! WOOT

Do a hard reboot - and hold down the OPtion-Command-P+R keys which will reset the NVRAM (non volatile)

Same issue — Dell P2415Q 4K monitor connected to Mac Mini 2018 via HDMI @ 60 Hz. Worked well on Mojave. With Catalina, -sometimes the monitor is detected and the Mac tries to use it, but never gets a picture — only a black screen. Sometimes it is not detected at all. Two other monitors (same model) connected via USB C to DisplayPort are still working fine, so the problem seems specific to HDMI.

I’ve tried switching to a better, 8K HDR compatible, HDMI cable but that made no difference. Resetting NVRAM didn’t help either.

C’mon, Apple. I could have this kind of fun with Windows. I was hoping to get away from it.

I use lg 4k monitor and i got same problem.

The way that i solve this problem is boot with commend + R, to boot with recovery mode.

It works usually (some time not works), and you can restart, then monitor is work with normal condition.

I can't believe this was not spotted in Beta testing. Shame on you Apple...

I have the exact same issue; Mac Mini 2018, connected via HDMI to my 4K Samsung. Works once in a while, but 9/10 it just turns on with no signal to the TV. The ONLY thing I found working sometimes, is booting into Recovery Mode, and then back into macOS.

After a few days of being p-i-s-s-e-d off, I finally found this page, and now I have it running using one of my ATDs using a USB-C -> DP adapter. I guess I can use a USB-C -> HDMI adapter for the time being, but I am really surprised that Apple is not on this like white on sugar. Do they not monitor these forums???

Hey, man. I've got the same problem, and my 4k monitor is also LG UD58A.

Whenever I use the HDMI on the mac mini, the monitor just left black and no signal.

After I use the usb-type c hub HDMI, the monitor can display picture. But the monitor is just 2k, not 4k.

Also frustate me...

I have 2018 mini. Two monitors. One hdmi the other usb c. Worked fine first two days. Now hdmi has no signal. Good thing I had two monitors or I would have thought my mini was dead. Getting a usb c to hdmi. Monitor is HP 25es.

It seems there are a number of temporary fixes for this problem. For me as long as I don't plug my 2nd monitor in on start up (USB C to vga) the HDMI is working fine. If I have my second monitor connected at start up I can't get anything on the HDMI at all . However I can plug the 2nd monitor in once it's booted up OK on the HDMI.

Still very frustrating as everything worked fine before the upgrade to Catalina. Hopefully Apple will have a fix for us soon.

Dammit! I thought it was all sorted out with a USB-C -> HDMI adapter, and it sort of is... except...

Did you know that the USB-C ports on the Mac Mini does not carry multi-channel sound? Well they do not. Hence, when you connect your TV to the Mac Mini via a USB-C -> HDMI adapter, you only get 2ch sound. So, if you are using Kodi for instance to play your multimedia files, the MP3 files work fine, but your Dolby Digital files do not.

The only multichannel sound interface is the HDMI connection, and it doesn’t work. Dammit!

How is it that after Catalina's been updated this issue persists? How is it that the BIOS/firmware/whatever hasn't been fixed?

The whole reason a good number of people bought the 2018 Mac Mini is the ability to output 4K, and at this point Apple is absolutely aware of the issue. They still haven't fixed the problem they caused. This is peak corporate FAIL.

Nothing works to get HDMI to HDMI working on my Sony XBR-49X900E. I've tried every idea thrown out in this thread, and I'm still using the USB-C to HDMI adapter I was forced to purchase after Apple bricked my HDMI port almost a month ago now. This is ridiculous.

It absolutely is NOT fixed. If anything, the situation is getting worse.

My 2018 MAC Mini (purchased in February 2019) worked fine with Mohave connected to an LG4K Monitor.

Like everyone else , after the Catalina “upgrade” it stopped connecting to the monitor via HDMI.

At first I could connect to a 1080p hdtv, then switch the cord to the monitor and it would work fine unless I shut down the computer. It worked if it went to sleep , but not shutdown. Then about 2 weeks ago it shut down due to a power failure.

Connecting to the tv first no longer worked.I called support and ended up with a senior advisor. Repeat p-ram resets and multiple unplugging and letting it sit, it eventually worked connected to the tv and I was able to switch the cable back to the monitor as in the past and it has worked. I hadn’t shutdown since and everything was fine until this morning. It apparently did an automatic install of 10.15.1 and shutdown. This morning I haven’t been able to get the monitor or tv (any display) to work no matter what I try. So here I sit waiting for Apple support to call. It’s Monday morning and I have work to do. This is getting REALLY OLD!!!

Same problem here,

I have the latest MacBook Pro.

I use a Acer ET221Q monitor for dual screen.

I bought a USB-C -> HDMI adapter to plug to it.

It was working perfectly with Mojaves but since the upgrade to Catalina the screen is not recognised, nothing happens.

I keep it connected anyway because sometime in the middle of the day it's working again until I shut my computer down. I tried to find a pattern but there isn't.

I tried resetting NVRAM, monitor detection, monitor profile suppression, changing USB-C ports.

I upgraded with every release they made in case they made a fix but nothing.

At this point I'm not looking for an answer I just want Apple to prioritize this issue and fix it ;)

I wish you luck,

Best reguards,

Lucien