No HDMI signal after update

I had to erase and completely reload my Macbook Air (early 2015) to get it to stop going into eternal slumber every time I turned my back. Sure annoying. And for anyone wondering, My mac started with High Sierra and it still made me reinstall Catalina. I never thought I'd see the day when I longed for my cheap old Windows machine but here it is and here I am missing it.

I upgraded my 2018 mini to Catalina a week ago. I noticed issues with my 3rd monitor not working & didn’t think much about it at first. But now it’s a real issue.

my only fix is disconnect everything but the hdmi monitor, restart, and it will eventually work after several “out of range” errors on the monitor. Then reconnect the other two monitors. Real pain in the *** since I keep my mini under my desk.

my 3rd screen is older so I use an hdmi to dvi cable. It worked flawlessly before Catalina.

I’ve seen usb-c to dvi cables on amazon but they all say they max at 1080p on Mac. Can anyone confirm this? My monitor is 1920x1200 so if they only do 1080, that’s not going to help at all.

of course Apple could always fix what they broke, but I’m not holding my breath on that one. Maybe we need the “Apple Pro HDMI Cable (just $999)”...

Workaround that works for me, (I'm using a Samsung 4k with HDMI to HDMI on a Mac Mini 2018): simply enter your password as normal even though you can't see what's happening, once the log in process begins the HDMI starts working.

Having same problem - updated to Catalina today and suddenly my two external monitors when black screen - connected via USB 3.0 mini dock. I can plug one monitor in at a time directly through USB and mini adapter which works, but can't get both screens up together through the dock anymore.

I've reset PRAM, and done everything others said worked through this thread but no fix yet to bring both screens back. Now getting new notification "USB Accessories Disabled - Unplug the accessory using too much power to re-enable USB Devices" - I have nothing even plugged in and this message just appeared for first time.

APPLE fix this - I rely on multiple monitors to work everyday. I hate to say it but I had to call Microsoft for tech support on a software issue today and they were much better than Apple has been lately...having second thoughts.

Installed the latest Catalina update overnight and my Dell U2413 connected via HDMI was working this morning. Rebooted to make sure and it came up fine - looks like some of the flickering of both screens which would occurred as the the HDMI screen woke up ( this occurred in Mojave also) may also be fixed. So two screens working again!

I have exactly the same problem with my 2 samsung 4k screens and mac mini all 3 bought in August 2019. There seems to be a problem with the new software os in connection with flat screens. Contacted apple support but they did not know of these type of problems and could not solve them.

Same problem here with my Mac mini 2018.

Just upgraded to Catalina, now same problems with HDMI 2.0 connection to my 4k LG display.

Only work fine with USB-C to DISPLAYPORT cable.

I HOPE APPLE DEVELOPS ACTULIZACION QUICKLY.

Lower resolution displays work fine even connecting via HDMI.

No problems with Mojave before.

I have this too. Apple help line said my Mac mini had a hardware issue. I have learned that they were not aware of this, but maybe they are now. I can only get an elongate desktop and it won't scale properly to my Samsung screen. I told them it was fine on mohave, but now I can't go back. The disk utilities won't give me the option to uninstall?

There are instructions online on how to downgrade to Mohave. You just need a flash drive. But you’re probably better off getting a $15 HDMI to USB-C / Thunderbolt 3 adapter like I did. Just make sure it’s rated for 4K @ 60Hz.

Same problem here with my Mac mini 2018.

Just upgraded to Catalina, now same problems with HDMI 2.0 connection to my Asus MX27UQ 4K display.

I do not have any USB-C to DisplayPort/HDMI cable. I can connect to my mac only via remote (VNC).

Please help me.

There is NO reliable fix, other then buying a USB-C->HDMI adapter, OR wait for Apple to release a fix. Sure you can try one of many suggested solutions, but they are only temporary, and once you shut down your Mac Mini, you're back to square one.

A week ago I let my 2018 Mac Mini update to Catalina, and like everyone else here, it bricked my HDMI port for 4K monitors. I bought the thing specifically because it could output 4K.

I wasted a night on a chat session, and that tech support person didn't have a clue. So I scheduled the next open Genius Bar appointment at my local store, waited 3 days, and then wasted my Saturday night making 2(!) trips to the store. On the first trip the tech person plugged my Mini into an old monitor... and of course it worked. He also plugged a wired keyboard so he could force select a monitor, and claimed that was the cure. So I went home, plugged it into my 4K monitor and... nothing. Back to the store, and he pretty much shrugged and told me to buy a wired keyboard so I could press CMD-F1 to select the output, which wouldn't have worked at all. He was just as uninformed as the earlier tech support person - now 4 days after Catalina's release and after this thread had been started. I wasted the remainder of my Saturday night researching, and I immediately ordered a USB-C to HDMI adapter, a part I have ABSOLUTELY ZERO USE FOR outside of this bug work-around.

I got the adapter yesterday, and like everyone else here, it works now. But no sound, so I plugged my soundbar into the headphone port. So much for digital surround sound...

This is all absurd. The ignorance of the Apply tech support people is absurd. Releasing this garbage firmware/software is absurd. I am completely unimpressed and furious at all my wasted time and trips to the store. And I've wasted money on an adapter that I otherwise did not need.

And the fact that Apple hasn't fixed this problem yet is the most absurd thing of all. I still can't use my HDMI plug, and I'm not all all impressed.

TOTAL FAIL

No! Even the new adapter, model A2119, does NOT guarantee 3840x2160 at 60Hz - https://support.apple.com/en-ca/HT207806

As a matter of fact the Mac Mini isn't even mentioned in the material from Apple:

Model A2119 is the newest model of this adapter. It supports HDMI 2.0 at these resolutions and refresh rates when used with macOS Mojave 10.14.6 or later or iOS 12.4 or later. It also supports HDR video in HDR10 and Dolby Vision formats when connected to a compatible playback device and display, TV, or projector.

• Up to 1080p at 60Hz
• 3840 x 2160 at 30Hz
• 3840 x 2160 at 60Hz with these devices:
  • 15-inch MacBook Pro introduced in 2017 or later
  • Retina iMac introduced in 2017 or later
  • iMac Pro
  • iPad Pro

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