Mac Pro 2019 monitor not waking from sleep

Further update: Connecting all three monitors via HDMI appears to solve the problem but then necessitates keeping both graphics cards installed, something I was hoping to avoid 😆

Next step... try all this again in Windows to see how differently that fails!

edit: thank you for reading along with my ridiculous troubleshooting liveblog, I hope it was less painful for you all than it is for me

I have the main 4K display connected to a TB port on the W5700X, the other two (1440p and 1080p) are connected over HDMI to the 580X (one via a HDMI to DVI cable). I've tried various combinations and this has been the least inconvenient because the two HDMI monitors wake reasonably reliably, and it's only the (thunderbolt to DisplayPort) 4K monitor on the 5700 that doesn't seem to wake up. Because that's the easiest monitor to wake manually, I've left it in this config.

I have tried running without the 580X in there, with two tb:dp cables for the two better monitors and the HDMI to DVI cable on the 1080p monitor, all running from the 5700 (on separate TB buses!) (EDIT: and that didn't work either, with any-or-all monitors failing to wake)

I have not tried running only a single monitor yet and I don't think I have tried using the top ports. I will the top ports to the list of things to try, which will be very disappointing if it works because those ports stick out like a sore thumb 😆 (I'm not sure which graphics card would control the top ports with both cards installed, but the Displays tab of About This Mac should show that)

One other thought is that the UPS is connected to an on-board (rear) USB-C port via a cheap USB-C to A adapter. Maybe (?) that (?) is (?) messing (?) with (?) the (?) Thunderbolt (?) bus. Too many question marks because I doubt it (??). UPDATE: No it's not, I forgot I had moved it to a USB A hub. There are no other Thunderbolt or USB-C devices connected. Hmm. HMMM.

Two of my monitors are pretty old, maybe they're just too ancient to play nicely. Sigh.

Thanks for your advice and this therapy session 😁

Updates for anyone interested:

• Main monitor (4K Acer via Thunderbolt to DisplayPort cable) does not wake from sleep if other monitors are attached. It does wake if it's the only monitor connected. When other monitors are connected, this one appears to wake briefly, then re-sleep as if it's hitting the snooze alarm. Like the Mac finds it, then loses interest when it finds other monitors. I can wake it up manually by pressing the menu button, which then puts everything right (other than all windows being moved because the monitor arrangement has briefly changed). I am trying to get into the habit of pressing this button before waking the Mac which is great because I never remember and so it is a constant source of frustration.
• Secondary monitor is a 1440p Dell. If it sleeps while connected via thunderbolt/displayport, nothing can wake it up except for unplugging/replugging the data cable. All buttons/touch sensors become inactive, including the power button. (These buttons work perfectly before it goes to sleep.) This happens whether it's a solo monitor or not, making me think that maybe it's a sleep mode incompatibility. Connecting over HDMI instead works fine.
• Tertiary monitor is a 1080p Acer. It is connected with an HDMI to DVI-D cable and currently has no problems. Previously it would fail to display an image sometimes, although the Mac thought it was connected and active (I could move windows to it). Unplugging and replugging the data cable solved this. Occasionally it displays only digital noise — static, not a mangled image. Like an untuned analog TV but higher res. Strange. I think it was having trouble locking onto the DVI-D signal. This monitor is very old and I do not trust it, unlike the other two. I am very willing to ditch this one but removing it does not seem to affect the other two, so it stays.

Other things I've tried:

• Detect Displays button does not help
• Eliminating possible ground loops by running everything off the UPS (usually I only run the primary monitor from UPS to save battery), which had no obvious effect
• pmset -g live to check for weird power management issues (all looks correct)
• Different combinations of monitors/ports/graphics cards/etc. There is always something that doesn't work properly.

At this point I really think this is being caused by a firmware bug in the Dell and a software/firmware bug on the Mac.

What I'm looking for, if this sparks any ideas:

• Relevant information about my situation and equipment
• Troubleshooting steps specific to the stage I'm at (beyond the basics, unless there's something glaring I've forgotten?? (or forgotten to mention))
• Error log advice - is monitor detection/mode switching logged anywhere? I can't see anything in Console, or if I can I don't know what I'm looking at or for.

Well ok, you mentioned "query[ing] the display" but not DDC specifically. No matter! My understanding is that enabling or disabling DDC/CI on these two monitors (which is disabled by default) is not affecting DDC itself, just the "Command Interface" extensions that enable the computer to control brightness, etc. Enabling or disabling the setting makes no difference to the symptoms. Disabling DDC/CI prevents the Mac from controlling the screen brightness.

FYI, the 4K monitor (when connected solo over TB/DP) wakes perfectly with DDC/CI disabled. Or enabled. Similarly, the Dell fails to wake the same with it on or off. 🤷🏼‍♂️

Edit: I don't know why I keep calling it "DDI" - I mean DDC 😐

OK! These cables are active USB devices and they show up as "Billboard"

I think we may have found the smoking gun...

Thanks for the suggestions, gang - no new info there unfortunately, I'd tried all the suggestions already as detailed in the original post, except for polarity which is a suggestion I'm not 100% sure what to do with 😆 I hadn't mentioned that I already have the ports manually selected on all monitors, no autoscan here, no sir.

Update for you all - I upgraded to the W5700X card from Apple and the problem persists. Monitors connected over thunderbolt (via a thunderbolt to DisplayPort cable) do not reliably wake from sleep. They cannot be found by "detect displays" and need to be manually woken. (impossible on the Dell, which appears to put its buttons to sleep as well. Sigh.)

It's very irritating because all my windows move themselves. Photoshop crashes on every wake, because the monitor it was on disappears. This all very much seems like a software bug in Catalina, rather than a hardware problem. So, I'm hoping for an update that fixes it. 🤷🏼‍♂️

Next thing to try is connecting ALL monitors over TB/DP with no HDMI connections just in case there's a port prioritisation issue or something. Surely it will wake my monitor if it's the ONLY monitor? We shall see. Failing that, please join my gofundme for three Pro Display XDRs (this is a funny funny joke).

That is an interesting theory! Is that documented anywhere by Apple? Even if it is correct, I don't think it applies here because, amongst other reasons:

• I am using 1 legacy monitor, or two if you count the HDMI which I don’t because they are non-adapted native ports. Even if you count hdmi as legacy, I’m not running more than two legacy devices
• The Thunderbolt/Displayport connection is the only one being used on the W5700X (so, no "electronic stress" on that card)
• The monitor-not-waking problem also occurs with only two monitors connected, both in Displayport over Thunderbolt mode
• DVI is 3.3v and that's the only "adapted" signal, which is running off an HDMI port. (The HDMI spec calls for 5v +-0.3v so I really doubt these were designed to only output a 3.3v HDMI signal)

I know I'm expecting a lot, wanting a computer to be compatible with any old monitor, but, like, that's exactly what standards are for 😆