Reasons for Inspiron 620s not turning on all of a sudden?

Hello guys, nice to meet you all. New here.

So I thought maybe someone could have the knowledge to deal with this issue I am having. This DELL Inspiron 620s my uncle has, stopped working all of a sudden. I did most of the diagnostics like memory, removing front usb panel cables (as suggested in another thread) and even the "paper clip test". But so far I believe it's the power button.

I read that the green light on the PSU = to good condition, so all results of diagnostics gave green light. However I am not sure about the amber color mobo light as I suppose it's to tell if it has power or simply "saying" there is a hardware problem (be it mobo, or cards).

He did tell me he kinda yanked out the cables of the desktop without properly shutting it down in a rushing attempt to get it to me quick (mother's day reunion) as I was originally going to do something else with it. So I believe it just pretty much messed up the system overall.

Any help is greatly appreciated and once again it was pleasure to meet you all!