No HDMI signal after update

Similar problem for me : mac mini connected to my old sony 65" TV ; was working fine with 10.14.

No display aft upgrade to 10.15.

It's work when connecting mac mini to an old 1080p.... quite disappointing; how do Apple test their new versions ???

Thanks to everyone for sharing their experiences. On one hand, I'm glad it's not just me. On the other hand, I'm sorely disappointed in Apple. I moved away from Windows to avoid this kind of frustrating, time-consuming, and ultimately expensive issue. Catalina should not have been released without at least validating that it didn't break and advertised feature (HDMI) on the latest Mac Mini.

Anyhow, I had been considering getting an eGPU before and though it might be a way around this mess. I got a Sonnet Breakaway Box and an RX 570 card, supposedly a supported configuration. But all is not well on that front either. During boot, after the Apple logo, the monitor connected through eGPU goes solid white. A little Googling shows that this too is a common problem with Catalina. Apparently only the more expensive Vega cards are working smoothly at this point with Catalina. I'm waiting on one of those from Amazon.

It upsets me because I too moved to Apple to get away from windows and to have a more fluid experience with my other apple products . iPhone 8 Plus , iPad Air 2 , iPad mini and iPad Pro . I bought a refurbished iMac 2014 model to see if I would like using a Mac and fell in love with it right away . I went out two weeks latter and bought a Mac mini 2018 model , New Lg 4K monitor external drive for time machine etc.

Things where running great until Catalina , spent two whole days trying to find a cure for the dreaded black screen . Not one Apple on line Tech knew what to do or even heard of the problem . One even said that I was welcome to upgrade to a higher end machine for only $400.00 and that would cure it .

Just by luck and frustration that my new machine was dead did I try using a usb c to Hdmi adapter. But this after many hours messing about and going back to Mojave and then reinstall Catalina over again . Now the mach is working great except for a few glitches that I expect in a beta release.

The funny story in all this is that the older 2014 iMac that when I first purchased had elcaptian on it the Mojave upgraded just fine. I ran a little slow for a while but I tweak some settings and its good to go .

I would expect this from windows , I had to buy a new laptop the last major upgrade because it slowed that machine to much .

Come on Apple you are better than this .

I got the same issue with Mac Mini2018 with a Dell U2718Q Display.

I have to use a USB-C o HDMI adapter to get the signal. Yes, using an adapter works.

But, if you remove the HDMI from the adapter to the original HDMI port on mac mini, it stills get no signals.

I am just list the issues here, so Apple tech-team can get more devices tested before publish the OS.

Tesserax wrote:

It would be impractical, if not impossible, to test every possible combination of hardware to verify perfect operation, .

I disagree. Certainly that's true for Windows PCs. In this case, Apple completely controls a limited number of hardware configurations and broke one of them. It should have been possible to test the HDMI port on their newest Mac Mini and all other supported hardware for Catalina. It's not a niche, cutting edge, or infrequently-used-combination-of-hardware issue.

Your assumption is that this is happening to EVERY Mac Mini. Every new iPhone release you hear about issues with activation, yet I’ve had nearly every version of the iPhone and I’ve never experienced activation issues. I’ve seen all kinds of issues reported through the years with Apple hardware I’ve owned and always wondered, “who are these people having these issues? I’ve never seen that with mine.” Well, here I am. First time in over 15years of owning Macs I’ve had anything but minor hardware issues. I doubt this effects every single Mac Mini out there. More than likely we all own Minis made on a particular day at a particular facility that did something oh so slightly different that caused this. Something Apple could have never caught without testing the new OS on tens of thousands of machines.

This exact problem occurred on 2 Mac Minis after updating to Catalina. Downgrading to Mojave by restoring from CCC clone did not resolve it. I suspect that Catalina updated some HDMI related firmware which cannot be easily be undone.

i have an active support case open. In the meantime, a USB-C to HDMI cable works fine, as it bypasses the HDMI output on the Mac. https://www.amazon.com/gp/product/B075V5JK36

I have just gotten off the phone with Apple Tech Support. The case got escalated, and they spend an hour collecting information.

APPLE KNOW ABOUT THE ISSUE, AND THEY CAN REPRODUCE IT.

The reason why they collected all the information, was to get as much as possible.

They are working on a fix, but it'll probably be a while. I am testing Beta 15 (19A582a) which I believe is 15.1 or perhaps 15.2, and it is still an issue here...

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 had a lot of issues too, so far the only thing that works for me is DP to USB-C, both monitors work fine with that. I have two HDMI to USB-C cables I was using previously with Mojave but they do not work at all. HDMI to HDMI, not working although if I use my laptops USB-C dongle in the Mac mini and plug an HDMI to HDMI cable in via that it works fine...

I believe that the issue of the HDMI to USB-C cables not working could be the cables themselves, they are made by Benfei, the first set I got didn't work and they replaced them with ones that did, so I suspect they were flaky at the start. As it happen the DP to USB-C are also by Benfei but newer.

Same. I noticed this first running the public beta and reported.

I have three 4k dell monitors attached (2 27" U2718q and 1 P2415q), one via HDMI to HDMI and two Thunderbolt to Displayport. Upon cold start, HDMI signal is not recognized and monitor goes to sleep and there is no waking it no matter what you do. I even replaced the cable.

If you shut down, unplug the two connected via thunderbolt and power on, the HDMI is fine. You can then plug in the two Thunderbolt monitors and everything is good. You can ever restart and everything is good - just seems to happen with other monitors attached via thunderbolt in my case and only on a cold start.

As a long time and avid Home Theatre enthusiast, and also someone who’s not into pop phrases, I just have to say that HDMI is far from a solid technology, and most who’ve worked with it for any amount of time consider it “a hot mess”. I am in no way saying this to excuse Apple from missing this problem, but breaking HDMI or at least crippling it, is pretty easy. The HDMI consortium creates a moving target to not only bring more advanced capabilities, but to allow manufacturers to sell new products; this puts us in a constant churn for new TVs, AVRs, UDPs, ATV, HD, UHD, 4K, 8K, HDR, Dolby Vision, Atmos, immersive audio, in a premium certified wonderland! Which is all to say it’s not bullet proof and $#!+ happens (again, I believe this should have been caught).

Someone had a theory that all of our minis were made on the same day, or had a unique part, or something else in common, there could be some merit to that. I’ve had a problem before Catalina with Mojave ‘waking up’ my monitor after the Mac was in sleep mode, often having to hit keys or click the mouse several times, I never had this problem with other minis or with HD monitors. Has anyone else noticed this with their 2018 mini and 4K TV/Monitor? Could this be something we have in common? Or rather something our monitors have in common in how they interact with the new minis HDMI? Looking for commonalities.

In the mean time I just received a USB-C to HDMI adapter (seemed I’d have more uses than a cable), and I can report another cheap workaround device for this HDMI issue. I’m hoping it’s a temporary solution as it now occupies my last USB-C port.

https://www.amazon.com/gp/product/B07JW7GT7H/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

I am using Acer KG241Q monitor to connect to Mac Mini 2018. During Mojave, it worked fine HDMI > HDMI. After upgraded to Catalina, HDMI > HDMI, USBC > HDMI > HDMI or USBC > DisplayPort did not work. I can't troubleshoot anything because there is no display to work with. I fear also that my SSD may crash as I forced shutdown it a number of times to try out the different ports. $&^$&$^ upgrade.

Resetting SMC and PRAM has resolved the problem of no connection being established with my Dell U2413 via HDMI - we will see if it lasts. The screen was recognised initially by the Mac mini after Catalina as installed, and then it stopped.

I was experimenting with Sidecar when the problem initially occurred and wondered if there might be a link - this seems (even?) less likely now - we will see. It looks as though the system could be corrupting the stored parameters in some way.