No HDMI signal after update

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.

On hold listening now trying to get a human to advise on this - - must be a lot of problems as normally they answer quickly - this is very unapple like to blow something this basic

They broke something that did not need fixing or so it seems - and shipped it without testing it or providing instructions on protocol... hmmmm

Have you installed the latest patch . 10.15.1

. It should cure the problem .

install the update with a USB-C to hdmi adapter which fixes the problem.

after the update completes and the system is stable then power down and back up with the adapter in place and then power power down and go back to the hdmi cable and all should be good.

i had been using the USB-C to hdmi adapter since the the move to Catalina and now that 10.15.1 is install my hdmi port works perfectly .

10.15.1 DID NOT fix mine. I did as others suggested. Reset SMC and NVRAM after updating. Still the same issue. I tried USB-C to HDMI cable, standard HDMI-HDMI cable. Nothing works except connecting HDMI cable to my UDB-C hub with HDMI. This makes no ****** sense at all.

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.

My HDMI connection works better with 10.15.1, but when it comes back from sleep, the image is still distorted until I turn off my monitor and turn it back on. So the update for me was an improvement, but not a total fix.

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.

Update: Loaded 10.15.1, cycled power after MacMini stabilized with USB-C/HDMI adapter attached, and switched TV input to the HDMI-direct connection (both from mini) and had video. Powered-off mini, unplugged USB-C adapter from mini & related HDMI input on TV (now just HDMI-direct signal). Turned mini back on and the HDMI signal remained intact. Several sleep cycles later and I still have full HDMI from MacMini (have recycled power 2x also). MacOS 10.15.1 seems to have repaired the issue on my machine.

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

“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.”

Obviously you haven’t read the last few pages, several if us, but not all, have had success installing the 10.15.1 upgrade. This is not just a reboot fix, but a shutdown, pull the power cord, power back up and it still works fix. Might there still be something wrong? Sure, but my system looks and acts the same now as it did with Mojave.

i agree that Apple has yet to fully identify the problem, and solve it in a way that fixes it for everyone, but something they did with 10.15.1 fixed it for some of us (or at least it appears to). Possibly something is similar about the monitors that now work, and different about those that don’t, I suspect there’s a third group that never stopped working.

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

Well it’s Wednesday... “senior level support” called Monday morning and we spent 2 hours on the phone with no resolution. My mini won’t connect to any display via hdmi or us USB-C or any combination of the 2. So they made an appointment for me at the “genius bar” for Monday night. They tried all the same stuff, plus several different monitors and also attempted to connect a display via thunderbolt. Nothing worked, so they ran multiple diagnostic programs (including some “super secret” program... whatever), the result... all hardware working. 2 hours later, NO DISPLAY, NOTHING MORE WE CAN DO. They said it’s definitely a software issue, and my case has been sent to engineering.

It wasn’t a pleasant experience, as the technician “genius” initially had a bit of an attitude and wanted to replace the motherboard and reinstall Mohave... would take a week, and my time machine backup wouldn’t be useable because it was created with Catalina.

I’ve ordered a USB-C to DisplayPort cable because they didn’t have one... my last hope to get my $3000 paper weight working again. At this point, I’m not sure how I would even get a “fixed” update on my computer since nobody can boot it up. I can’t even begin to convey the level of frustration, disappointment, and quite frankly disgust I feel toward Apple at the moment.

Their latest updates (including IOS) have been anything but trouble free. I don’t know what’s going on out there lately but it’s not good and some senior level people need to be called out. To have such a major OS released before it was ready just to make an artificial deadline is a very clear sign of a negative change in the culture and direction of the company.

Well I received my cool new $20 USB-C to DisplayPort cable from amazon, plugged it in, and guess what!

My 8 month old Mac Mini... STILL DOES’T WORK! Hey but when I push the power button it does get this cool little white light on the front. I have the absolute coolest $3000 paper weight around!