turns on for a second

(Sorry for the repost but I need help) My PC has been having an issue where it turns on for a second then off immediately. This started happening after my power cut out once. However the first time it happened, it waited an hour or so and it was able to boot up fully without any issues. I...

I am using a z420 motherboard and when I power it on it turns on for a second then shuts off, then continues with 4 beeps. This indicates a power failure, but I don't understand if its the power supply or the motherboard. I used the paper clip trick on my power supply and the fan spins. I...