No power
A short or kazooed component including power supply.
I'm not familiar with machine. Is there a fuse?
No?
If you have kids, turn machine upside down to see if anything rattles. No kidding, kids can make a piggy bank out of anything.
No?
Remove all cards, then try. If it works, add in boards until you've found culprit.
No?
Disconnect everything from power supply except system board. If that works (power supply fan comes on) try reconnecting other devices until found.
No?
Disconnect everything (including system board) and connect only one device, e.g. hard drive.
Yes? Faulty system board.
No? Faulty power supply.
Regards