Hello, I need help with the same.
However, I know a little better about it.
So I think you will help me.
Starting off, the monitor does not detect that it is turned on (cables are connected) when the computer starts up.
Does not read from the hard drive.
Everything happened after my colleague installed the system on his hard drive (my computer served as a skeleton for installation), after plugging in, the information that "the drive is not connected" appeared
Although the power and cable to the motherboard was properly connected. I rummaged in the bios and turned on the Windows 10 install. Then I pressed repair and turned on the backup. I got an error with Windows Defender and after rebooting the screen crashed and the computer still does not read the hard disk.