PC Won’t Post

My sons PC which was working fine, has stopped completely since it was removed across his room.
Everything is securely plugged in and there is power at the wall outlet feeding his surge protetion power strip (which is functioning correctly). Why, all of a sudden it’s not booting is a mystery to me. My son mentioned that it may be overheating but, I can’t get into BIOS to check the operating temps. Since he hasn’t ever changed the BIOS button cell battery, I was wondering if that might be the problem. Before I open the PC case up, I’d like to know what else to look for. Yes all the fans are working and there are no cables interfering with the CPU fan or any other for that matter.