Question PC won't boot --- Z390 has yellow LED next to the M.2 slot ?

[MaTr3x140!!]

I was helping my friend swap her components into a new case and her PC won’t boot now and she has a yellow led just above the m.2 slot at the bottom of the motherboard. I’ve had her pull the gpu and try booting and that didn’t work and I’ve had her check the cpu cords to make sure they were plugged in properly. Any ideas what else could cause issues?

 

[Deleted member 1272431]

Some questions to better understand the issue:

1. The computer was working in the other case and after moving it it does not boot, correct?
2. You do not get any screen? No POST either? Just black monitor with no signal?
3. Does the motherboard do any sounds (beeps) on startup?
4. Have you connected back all power required by the motherboard?
5. Did you remove the RAM in moving the computer?
6. Have you tried switching PCI ports for the Graphics card?