No display on every other install...but ONE is working. Where do I look to find out why?

Background:

Debian Linux - Bookworm Using Lightdm and XFCE

I've run xrandr --verbose

It looks like HDMI-1 is being detected on the working unit, but not being detected on the non-working ones. If I take that monitor and plug it into a non-working one, it doesn't work on that device either. If I plug a completely different monitor in, it works fine.

I'm trying to troubleshoot, but having issues trying to determine where the fault lays. Obviously it should at least detect the monitor when it's connected. It's a 5" mini screen. All of those screens work fine when I connect them to a different system running Windows.

I'm not sure if it's a driver issue, configuration issue, or kernel issue. Where should I start looking?

I've had a sharp learning curve with Linux. I've been at it for less than a year, so still have a lot to learn.

Thanks in advance!