There was a recent power outage (I'm not sure of the nature of the outage) that turned off my PC. I reset my power strip and PC power supply, pressed the power button, but the computer did not turn on. I verified that power was flowing through the power supply because my graphics card had lit status LEDs. The motherboard did not appear to have any status LEDs lit.
After some research, I decided to try manually "jumping" my motherboard. I disconnected the cabling from the case and manually shorted the PWR+ and GND pins with a screwdriver. This turned on my PC, so I killed the power from the power supply. After reconnecting the cabling to the case and switching on the power supply, the power button started working again. The motherboard still did not appear to have any status LEDs lit for any of this.