Tried 3 different disks separately. NVMe ssd, 2.5" ssd and a 3.5" spinning disk.
having no HDD/SSD to boot from is fine, that doesn't matter, but i'm just saying it's stuck on Green because there's no OS to boot from, or probably because it's stuck on first bootup screen, new motherboards will get stuck on a screen that tells you to press F1 to enter BIOS or something like that.
once it finds an OS to boot, the Green light will go away and it will be white instead.
i'm fairly certain that it's your monitor, maybe it doesn't support weird resolutions that the BIOS runs at, but will appear once you boot into windows, i've had experiences like that before, or maybe try a different cable? cuz HDMI is weird with resolutions