No HDMI signal after update

Same problem here. I connect my Mac mini 2018 to my Samsung TV - UN49MU8000FXZA. No HDMI signal after turned off and on again. My TV has 4 HDMI ports and none of them works. I do not have USB-C to HDMI adapter, so I would buy one soon.

I spent a lot of time talking to Apple Support the last couple of days making sure they are aware of the issue. Today they told me that Apple is aware and that they are investigating. For the time being, I’ll keep using my HDMI to USB-C adapter as a workaround, and I’ll try to go back to HDMI each time an update comes through.

I have the same issue. Had multiple online chats with advisors last night performing resets, booting into safe mode, reinstalling Catalina, etc with no positive results. I am driving two LG 32UD99 4k monitors. One via USB-C and the second via HDMI since I have another system connected to the USB-C input on the second monitor. The HDMI from the Mac mini is non functional after the update to Catalina. Apple tech support finally set up a phone call for this morning, supposedly with an Engineer. However, it was just tech support trying to get me to perform the same things again, which I refused to do, so they forwarded me to senior tech support person, but still not an engineer. He took more info and tried a couple of new things like deleting a plist file, but still no positive results. At least they acknowledged that there is an actual problem, but no solution. I'm rapidly losing faith in software updates for all Apple products and considering going the route that my wife went with, which was to get a Surface Pro instead of staying in the Apple ecosystem. For the time being I will drive both monitors via USB-C which is inconvenient since I do need to physically swap the USB-C cable from my other system when using the Mac mini. Hopefully they will solve this soon.

“I think Apple is going to come with a recall for all of our computers. It is looking like the software is damaging the ports. Did someone tried to go back to Mojave and try the ports fro HDMI??“

I believe that’s been mentioned, the discussion was that along with Catalina there was a firmware update applied to the hardware, so that even going back to Mojave did not solve the problem. If that were the case we might expect a firmware and software fix.

Only 30 Hz possible (https://support.apple.com/en-us/HT207806)

Intel UHD Graphics 630:

  Chipset Model: Intel UHD Graphics 630

  Type: GPU

  Bus: Built-In

  VRAM (Dynamic, Max): 1536 MB

  Vendor: Intel

  Device ID: 0x3e9b

  Revision ID: 0x0000

  Metal: Supported, feature set macOS GPUFamily2 v1

  Displays:

LG Ultra HD:

  Resolution: 3840x2160 (2160p/4K UHD 1 - Ultra High Definition)

  UI Looks like: 1920 x 1080 @ 30 Hz

  Framebuffer Depth: 30-Bit Colour (ARGB2101010)

  Main Display: Yes

  Mirror: Off

  Online: Yes

  Rotation: Supported

  Adapter Type: Apple USB-C Digital AV Adapter

  Automatically Adjust Brightness: No

  Adapter Firmware Version: 2,35

Adapters don't solve the issue with a 3 monitor setup. It appears no matter what you only get 2 monitors working on USB-C and one on HDMI.

Unless someone has a combo working with 3 USB-C ports, let me know.

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.

I had the issue where after upgrading my external display would just show a blank screen. The instructions at site below fixed my problem:

https://appletoolbox.com/external-display-shows-black-screen-macos-catalina-and-other-issues-fix/

Basically I had to enable my display driver.

Hello everybody,

Today I noticed that 10.15.2 was released and I decided to give it a try.

I fully cleaned my Mac mini 2018 and installed Catalina from the internet completely new.

Finally I saw no more issues on my 4k Samsung anymore!

No issues during the installation and no issues after the installation.

Comparing the adapter firmware I recognized that it was now upgraded to version 2.16 with 10.15.2.

I hope that everyone will now be able to solve the nasty HDMI issues for Catalina and Mac mini.

I keep my fingers crossed.

OMG I think they partly fixed the issue. I upgraded to 10.15.2 last night with no luck. I still had to use the three power button trick to enter user name and password. Shortly after that the screen comes on. I seen the post today about the display firmware and I didn't check mine. I checked and there was no firmware number. I did notice that it was recognizing my monitor as a 5K monitor when it is only a 4K monitor. I had switched to a display port adapter video cable, because I couldn't get HDMI to work at all. I switch the cable back to straight HDMI to HDMI and it appears to work now. The display version is now showing and has been updated to 2.16. I've rebooted a couple of times and it brings me to the login screen that I can actually see. This is more progress than I have seen since the initial upgrade to Catalina. Here is to hoping that the issues are gone now! :)

Having exactly the same problem with HDMI. Have to unplug other monitor first, then boot up,etc etc. Needs fixing. Come on Apple.

My cure was usb c to hdmi ....

wonder how they beta tested this thing before released..

Same problem here. MacBook Pro (Retina, 15-inch, Mid 2015) with Iiyama HDMI external screen, no Signal Detected after the OSX Catalina update. Please fix this bug...

Same problem here.

[Mac mini 2018 + HDMI + Samsung 4k display]

Use USB-C to HDMI as a workaround now.

Please please please fix this issue, thanks.