My pc won't start after randomly shutting down

[Yous191]

today I came home from school and turned my PC on, went to the toilet, came back and my PC had shutdown. I went to turn it back on but it would not start. I know this is not a power problem as there is a light at the bottom of my motherboard so I know there is power in the PSU. I have tried using different cables but this has not helped, as well as using different outlets around the house.
How can I solve this? Any help would be appreciated

 

[ArthurST]

If you know which cable goes to the hard drive try moving the cable a little, maybe even disconnecting, but plug it back correctly. Also try moving the RAMs a little, don't disconnect them. Hope that helps.

 

[Ezy Ryder]

Happened to me before. I just plugged all PSU cables out and plugged them in again. Also clean PSU if you can.