HP Power supply flashing green light
This is an easy fix so here you go nice and simple:
Problem: Your motherboard circuit has been cut.
Causes: Power disconnected during operation. Power outage or short in the surge protector.
Symptoms: Flashing green light on both motherboard and power supply. System will not power on.
Step 1: Ensure that both the power supply and the motherboard lights are flashing green, not solid or off.
Step 2: While the power is on, disconnect the power supply from the motherboard. This connection is the largest of the connections and should be listed as the 'P1' or 'Primary' power connection.
Step 3: Wait until the green light on the motherboard stops flashing and check to ensure that the green light on the power supply is now solid. If it is not solid, disconnect the power to the power supply and wait until the light turns off completely. Then reconnect, it should be solid now.
Step 4: While the power is on, reconnect the P1 connection to the motherboard and you should now see that the light on the motherboard is solid.
Step 5: Power on your PC. The problem should not persist.
Warnings: If the power supply light remains flashing after you have restored power to it while it is disconnected from the motherboard, it may be a system failure in the power supply itself requiring replacement. Always be careful when working with an active or live power machine.