No HDMI signal after update

This $15 adapter worked for my LG. I can get full 4K @ 60Hz, though I choose to keep the resolution to 1080p @ 60Hz simply due to the size. I did test the 4K resolution though and it worked fine.

USB C to HDMI Adapter (4K@60Hz),... https://www.amazon.com/dp/B07HVQQPYK?ref=ppx_pop_mob_ap_share

Ok, just got a 2.0 usb-c - hdmi adapter. Works! Reboots. Hope this helps. Apple told me my computer was bricked and needed service. Just do this. They didn't even know they had a problem. Who is in charge of testing.......?

Thanks for all the help here on this board. Super stressful situation when you are trying to run a business.

T

I have a *similar* issue.

The issue that I have is display distortion.

Mac Mini 2018. Samsung UH750 monitor (4K). There are two HDMI ports on the back of the monitor. HDMI 1 is for 30 Hz, HDMI 2 is for 60 Hz. No problems when using HDMI to HDMI cable connected to HDMI2 with Mojave. However, the same configuration on Catalina causes the display to be severely distorted.

I've tried an NVRAM reset -- did not work.

I've tried plugging into HDMI 1 (30Hz) -- works but is suboptimal

The *ONLY* resolution I have found is to manually cycle through the input sources on my monitor. When I cycle back to HDMI 2, the distortion goes away.

Still... this is a very annoying issue to have to manually cycle every time the system boots up.

I expect more from Apple.

I had the same problem after I finally got it in recovery mode. I have u28e590d Samsung 4k monitor and the only way I was able to get it all the way back to normal was using thunderbolt usb-c to hdmi 2 (60hz 4k(2.0) hdmi) adaptor and I have not had to manually cycle my monitor. You could try an SMC reset if it continues. To be clear, I am using HDMI 2.

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'm not exactly sure what changed, but fiddling in Displays and going to AAA

explicitly seems to have turned things back on -- in any event, Built-In Retina

Display does not work even though I'm sure that did before.

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.

So I upgraded to Catalina about a week ago on my Mac Mini 2018. I'm driving 3 LG 4k displays (2 via usb c and 1 via HDMI). Absolutely zero issues with Mojave with this setup. Initially everything worked great after I upgraded to Catalina, then just today my mac mini froze and rebooted, and my signal to HDMI was gone. The 2 usb c displays work with no issue, and the mac mini recognizes the display in the HDMI port, but there is no picture. I ordered a usb c to HDMI adapter just this morning (as others had suggested as a work around) it arrived tonight (love amazon) and I plugged it in and it worked. Although there is a big problem...you can't drive 3 4k displays using just usb c on the 2018 mac mini...so only two work at the moment. I've tried all the solutions in this thread, pram, nvram, safemode, smc reset...nothing is bringing back the monitor attached to HDMI. I'm not going back to Mojave, as I've read that also does not work. I'm just stuck hoping Apple releases a firmware or macOS update to fix the problem. I'm still at a loss as to why it was working just fine for a week, then all of a sudden nothing.

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:)

“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.

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.

Update: I happen to catch on another forum that this workaround seems to kick the HDMI back on for 4k@60Hz. In my previous post I mentioned my setup as (2) 4k monitors running on usb c and (1) 4k monitor running on the HDMI port. The workaround that is now working for all 3 monitors is this: (1) monitor running directly into the HDMI slot, (1) monitor running directly into a usb c slot, and (1) monitor running into a usb c to HDMI adapter. After a SMC reset...all three monitors now working again on my mac mini running Catalina.

My connection from the USB C port to HDMI worked fine under the previous operating system, Mojave. However, since I upgraded to Catalina on 20 October 2019 it has ceased to work. I see from posts on the Internet that this is a know fault. I wish to know when Apple proposes to release a bug fix to cure this fault.