External display not working after installing MacOs Catalina

do you still have a Driver for the:

HP Elite USB-C Hub

Spent hours trying to work around the issue:

If both my projector and Mac mini 2018 are off, if I first switch on the Mac a minute or two before the projector, it’s as if the Mac HDMI output does not trigger/jog/activate the HDMI output signal.

The signal may not be being sent by the Mac, and/or’s not being picked up reliably by the projector.

If the projector is first switched on and given 1or2min to get to the No Source Found screen, and then the Mac mini is switched on, the Mac’s HDMI output signal triggers/jogs/activates and displays on the projector.

The only thing which works fairly reliably I’ve found is over the Mac mini’s Thunderbolt/USB-C port to HDMI input on the projector, instead of the HDMI both ends.

I’m trying to diagnose a new 2018 Mac mini I purchased from Apple new November (came with Catalina), outputting from the Mac Mini HDMI socket output is not reliable.

The HDMI output to an external display, is in my case a newly bought (end of 2019) Optoma UHD40 projector which otherwise is no problem, it works -I’m using to type this on.

At Apple support’s guidance, I’ve reset the PRAM/NVRAM with Command+Option+P+R right at startup, and reset the SMC. Didn’t help.

I followed Apple phone instructions to partition, actually we had to add a new volume called ‘Test’ on the internal Mac mini SSD.

Catalina download from the App Store said Gateway error, actually we had to startup in the Test partition to successfully download Catalina.

I created a new user account on this new Test partition of the internal SSD, but the HDMI external display issue still remains probably a software/firmware issue introduced with Catalina.

I’d try installing Mojave to check, but getting the download to work it just sits there, maybe too busy.

It would restore confidence in the quality of macOS if Apple got to the bottom of this issue at least before/for the next major release of macOS.

Duet, SideCar to an iPad don’t solve my underlying problem but may help get out of a bind once logged in if the screen goes blank.

In the meantime I’ve gone to Energy Saver system pref and ticked ‘Prevent computer from sleeping automatically when display is off’ which reduces the chances of having unsaved work left open which I can’t see and have to force power-off if the screen doesn’t back come on.

Thank you

I should have added that when I’ve booted the Mac before the projector and there’s no display image, but I know it’s at the login screen. When I login blind the Mac triggers the HDMI output signal and the display comes on.

To your point:

The UHD40 does not have those options/settings to change/help the situation which seems to be tied to Catalina not Mojave.

Mac Mini in this case, so no built in display. If To use Duet on startup that requires Auto-login to be set, that requires File Vault to be switched off. Essentially plugging in and switching on the Mac Mini has no password or FileVault security, or order for Duet to be used. Knowing it’s at the login screen once started up, it’s more secure to have a password and just blind-type the password which then activated/triggers the HDMI signal and the display comes on.

Of the four ways:

• at startup:

I switch the Mac mini on *after* the projector to work around the no signal issue of switching the Mac on *before* the projector.

• at wake from sleep:

I’ve checked all the UHD40 projector options, including the 7 different HDMI EQ settings, and turning on/off Auto Source. No image results.

• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go:

I’ve tried removing the Mac mini HDMI cable from the Mac mini output, left for over 5 seconds, reinserted - nothing results.

• on invoking Option-(Detect Display) button in Displays preferences

 I’ve tried the option-Detect Display button in Display preferences: nothing results.

As I say, I switch the Mac mini on *after* the projector to work around the no signal issue of switching the Mac on *before* the projector.

Or login-blind which again triggers the Mac mini to produce an HDMI output bringing on the screen.

I can work around the startup issue, but that's not so reliable.

Also, sometimes when the Mac goes to sleep I wake it up (my mouse lights up so I know it's awake) but the projector says No Source Found. Once I blind-login again it shows up.

I wonder if HDMI 2.0 version or HDCP version 2.2 have anything to do with the no HDMI signal issue?

Mac mini tech specs says it has an HDMI 2.0 outport. Not sure about HDCP.

Optoma’s stated cable length max range is 15’ to 25’, I'm well within that:

•Mac mini HDMI port: I’ve tried a 16’ (5meter) cable: 4K HDMI 2.0 Cable - UHD Lead 60Hz 4096 x 2160p HDR Cord Ultra HD 4x4x4 18Gbps - HDCP 2.2.

•Thunderbolt port: I’ve tried a 9’ (3meter) cable: USB C to HDMI Cable Thunderbolt 3 Type C HDMI 2.0 4K 60Hz.

For scale of macOS interface I’m using it at 1080p.

—

Based on the dozens of other comments since the original post, this issue started without any other changes than users upgrading from Mojave which did not have this issue, to Catalina which does have this issue. Surely that major macOS version factor speaks for itself?

Apple sent me a:

USB-C digital AV multiport adapter-ZML

I've just tried plugging the USB-C digital AV multiport adapter in to one of the Mac Mini's Thunderbolt output ports, and from the adapter's HDMI output into the projector's 60Hz 4K port. With the same steps as previously checked and reported on page 9 of this forum, with Apple's adapter what's changed is:

If the Mac mini 2018 is booted up first (e.g. about a minute or more) before the projector is switched on, the Mac with this new adapter now *does* produce a stable HDMI output signal which the projector picks up showing the login screen.

Unfortunately the adapter's HDMI output is significantly lacking in contrast (blacks displaying grey, I've checked the HDR mode is off as this can be a factor, but this option's no longer showing in Display) but it's no help, and the adapter's 30Hz, not the 60Hz the Mac's Thunderbolt and HDMI output do without the adapter.

I've gone back to using the Mac mini's built-in HDMI output without the adapter, just being deliberate to work around this issue by allowing the projector to switch on and get to ready at the No Signal stage, then turning the Mac on second/after the projector, which on startup produces the HDMI output signal which is picked up by the ready projector.

Thank you Apple for providing the adaptor, given it's grey 'blacks' and 30Hz issues noted above I've no need for the adaptor. Based on user's upgrading from Mojave to Catalina triggering the issue, Catalina seems to be a contributing factor, so maybe the issue could be resolved in terms of Catalina software update, or a firmware update instead of sending out physical adaptors? Thank you again anyway.

Your point about upgrading drivers for adapters is taken, but many others have previously posted in this thread descriptions without involving adapters, where upgrading from Mojave to Catalina triggers the display issue, which according to an Apple chap who asked me to do a timing snoop, seems more to do with the video output timing changes associated with Catalina.

Update. I think the problem is with the HDMI in Catalina. I had an older monitor that didn't use HDMI, and it is working fine. On another thread, several individuals are having problems with HDMI plugged into their MacMinis and external monitors and Apple is supposedly looking into it.

Hmmm....Strangely enough, it seems that the USBC port you plug the monitors into may also be causing the issue.

When I had it plugged in to the port furthest away there was no monitor detection.

However, when I plugged them into the port closest to me, it seemed to detect the displays straight away.

Perhaps, try changing the ports around to solve the issue.

APPLE PLEASE FIX.

I have this same issue. My 2018 Macbook Air no longer detects external monitors plugged into USB-C. I am on latest update. It worked fine before the upgrade after Catalina, and has not worked properly ever since. When I plug it in, it takes anywhere from 30 mins to 2 hours to detect the monitor is there. The normal monitor is an official Apple one (though a bit older). USB-C -> Thunderbolt adapter but the problem also happens with any other monitor I've tried. All the monitors work fine with other machines.

Detect Displays does nothing. I have reset the SMC. I have tried switching ports. Nothing has made a difference.

I bought my iMac about 2 years ago and shortly after connected 2x HP 23er displays with no issues, even after installing Catalina.

Oct2019 I moved and didn't turn it back on until Dec2019/Jan2020. Had the folder with the question mark, so I reformatted the drive and reinstalled Catalina, they still worked.

Last week I decided to take it in and have them reformat/reinstall. They installed Mojave back on.All 3 displays still worked.

A few hours ago I upgraded to Catalina and now both of my externals won't turn on. Well one does once in a while. Maybe there was an update that's interacting with the USB ports or drivers? I've tried the power cycle as mentioned and clearing ram, no luck.

Following to hopefully read a solution or I'll take it back and stick with Mojave.

After doing everything in this thread with no luck I started thinking. The turning on after a while, no signal etc reminded of a Vizio tv I had. It did the same thing on most devices and was some sort of signal incompatibility issue. I started wondering if they(Apple) are changing something with the signal transmission as their OS's progress.

Long story short, I bought a newer HDMI to USB-C and it's working (the VGA to USB-C did not). Tried it on both external monitors from both USB-C terminals on the back of my iMac and restarted the machine.

I'm about to order another one and try them both at the same time and see if they sustain connection. I'll let you all know. I'm using https://amazon.com/gp/product/B075V5JK36/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

I don’t think it will work if it is a dock that was made to connect to a traditional usb 3.0 “A” port.

macOS never had real support for display connections over legacy USB (by legacy I mean before USB-C)

Some trickery made some docks work via unpublished API - there were long threads you may find if you search these forums for “displaylink” - but these were not Apple sanctioned methods and kept failing more or less with each OS update, requiring further trickery to revive.

I just took delivery of a 2020 MacBook Pro and plugged it into my new LG Ultrawide monitor using Thunderbolt 3 cable from the MBP box. Apart from power, nothing, just the ‘No Signal’ message, no sign of the display on the MBP either. I tried almost everything on this thread Over and over till 1am.

This morning I phoned Apple Support, no help except ‘talk to LG’.

With little expectation I phoned LG. After the usual rehearsal of solutions I had already tried, and at the end of the call the LG assistant casually asked if I was using the Thunderbolt cable provided with the monitor? I quickly swapped the cables over to the LG cable and instantly the monitor fired up in all it’s glory... Moral, don’t assume the very expensive Apple supplied Thunderbolt cable is appropriate in all cases.

This is the fix you used, right?

You used a separate ThunderBolt cable to connect to the display's ThunderBolt port (which feels like only an OUTPUT) and left the main display input cable unconnected.