Ok,

My new computer came in yesterday and I've installed all of my software.

Hardware:

CPU: Ryzen 5 3600x
MB: Asus TUF x570 Plus
Ram: 16GB
GPU: NVidia GeForce GTX 1660 Ti
SSD: 512 GB

Issue: Four Monitors connected in this way to the GPU listed above:

Dell U3011 - connected via display port cable
Dell P2012H- connected via HDMI to DVI-D converted cable
Dell P2012H- connected via DVI-D cable
ViewSonic VX2439wm- connected via HDMI cable

My GPU has those four inputs: DP, 2xHDMI, and one DVI-D

All monitors and GPU have been updated with the latest Windows supported drivers for their models.

All monitors run at the correct resolutions and work fine while on but when I shut down the computer or put the computer in sleep mode all monitors go into power saving mode/sleep mode except the Dell U3011 connected via the display port cable.

The Dell U3011 black screens and has an icon which says "no Display port cable detected" which moves across the screen.

I can manually turn the monitor off but in the past when this monitor was connected via a DVI-D cable on my old system it would go into Power Saving Mode and sleep just like my other two Dell Monitors.

One thing I've also noticed and tested which is different than my last PC setup. I have a UPS and tested a power outage situation on this "new" PC. If power drops the Dell U3011 goes black for about 1 second before coming back on. This didn't happen on the old setup. This makes me believe there is some sort of power issue with the GPU sending the signal via Display Port to this monitor which could also explain possibly why the monitor doesn't shut down when I turn off my CPU.

Any ideas on how to fix this issue? This Dell monitor is almost a decade old and I did find some threads online that discussed this as a problem with Dell monitors when connected via HDMI or Display Port. Maybe it is just a problem with compatibility but just curious if anyone in this thread has a tip that might fix it.

Just to add I tested something just now.....

I took the DVI-D from the side monitor, removed the Display Port cable from the trouble monitor, and put the DVI-D cable into the Dell U3011. Shut down my computer and the Dell U3011 instantly went into Power Saving Mode and turned orange on the Power button rather than staying blue and displaying a missing cable message.

So it seems it has something to do with the Display port connection rather than the GPU

could be a setting in bios (uefi)
something to do with power management
maybe on the PCIE
or the gpu driver version you're on right now

Thanks for the suggestions ionutd. I'm not sure what to change in the bios settings.

A couple new tests with Dell U3011 connected directly to the GPU via a Dual DVI-D cable. (Just like on the old system)

As mentioned above at shutdown in this scenario it does turn off the screen but I noticed the light on the power button is a slowly blinking amber light rather than being a solid amber light as it is on the other monitors. If I turn on the computer from here the bios screen loads on a different monitor other than the Dell U3011 which is my main monitor in windows settings. The Dell U3011 stays sleeping until the Windows login screen, and then the power light turns blue and the Windows log in screen is loaded on my main screen.

I'm not sure what to make of this or what to test now. I had considered just buying another converter, display port to DVI and setting up the monitors in that way but it's not performing the way I want it to on start up and something seems off.

Is there some way to force the bios to load on the Dell U3011 while the other monitors sleep at startup?

If the 3011 works with dual link DVI on the card as expected, keep that as/is and connect one of the smaller monitors via adapter. Most HDMI/DP to DVI adapters are single link and limited to around 1920x1200.
The issue you're seeing is most likely in the monitor firmware and not something you can fix without replacing the monitor. I wouldn't buy a new monitor dependent on dual link DVI, but you've got a working option for a still perfectly nice monitor so I'd just roll with it.

Purchased the adapter and this fixed all the problems. All monitors display in their native resolutions and sleep and the issue when simulating a power outage, ,all monitors stay bright throughout the process. Thanks for the suggestion.

Only thing that's not really an issue but I'd like to setup differently would be to have the bootup screen load on my main middle monitor. Currently that screen is loading on my side monitor which is in portrait mode, so it's also turned sideways and looks a bit awkward during the startup process. That screen is the one now using the DVI adapter connected to the display port.

The priority for boot display seems to be Display Port>Hdmi>dvi. Is this something I could be able to change somewhere in the settings of the bios?

Windows screen loads fine on my primary monitor first but if there was someway to also force the boot screen to display also on that monitor I'd like to do it. Either way it's cosmetic at this point so I'm happy my main concerns were fixed. Thanks.