Monitor + Cable + Onboard Video... What's Wrong?

I built three computers that have identical hardware and an identical cloned Windows drive, except one of them has a GTX 1660S. I have a Samsung 226BW Monitor (manual). It has a DVI-D and VGA port on it. My graphics card has HDMI and Display ports. So I needed to purchase a DVI-D to HDMI converter. I used an HDMI cable I had lying around the house, which I know nothing further about.

The 1660S worked with my monitor just fine. The two computers using on-board video (Asus Prime X570-P, manual) do not show video, but thanks to sound I know they boot into Windows successfully. The monitor has a source switch button to go between VGA and DVI-D. When on VGA it says I should check the cable. When on DVI-D it flashes between a Analog and Digital message a couple of times and then the screen goes Black (just like when Windows shuts off my monitor after being idle too long), with no error about the cable at all.

The cable and DVI to HDMI converter obviously work because of the success with the 1660S system. With two motherboards having the same issue, I wouldn't think the onboard video port was faulty. I checked the manual for the motherboard and on page 8, the only place it mentions anything about HDMI, it states:

The line about VGA output support. Any chance that means this won't work with DVI-D? That I need a VGA to HDMI converter instead? I wouldn't think so but I'm grasping at straws here. The 1660S has a HDMI 2.0b port and worked, so I imagine my HDMI cable is capable of displaying video to a HDMI 1.4b port. I'm not sure what else to try. Any ideas on what else I might try to diagnose this issue?

UPDATE
I acquired an Asus Pro Art Monitor and used the bundled HDMI cable with it. It reports there is no HDMI signal. This rules out the DVI-I converter, the HDMI cable, and the monitors as potential causes. There is obviously an issue with the motherboard at this point. But two computers have the same issue, so it seems unlikely the HDMI port on the motherboard is faulty. What am I missing? I just don't understand what could be wrong here.

 

I have confirmed that the motherboard only supports APU's, not CPU's like the Ryzen 5 3600x I have installed.

 

Whoops. I meant that the "onboard video" is only possible with an APU installed in the system. That a CPU and a monitor hooked up to the HDMI port on the motherboard will not provide a video signal.

 

Just for some clarification:
In the motherboard manual, it would explain the ports available on that particular components, in which case it is usually a hdmi and vga port.

You can only obtain a visual output (in most cases) with a gpu whether it be discrete or integrated. If it doesn't have an APU, then connecting it to the motherboard would produce no video signals.

By an chance, just to make sure this isn't related to Windows 10 possibly becoming corrupted during the cloning process, are you able to access the BIOS?

 

I apologize for the late reply Jared. No, I was not able to see the POST process, nor access the BIOS. Thank you for your help and suggestions ^_^