Motherboard shuts off and red light


My motherboard is a gigabyte z370 hd3 got it cheap because 1 pcie slot is broken or so the guy said, so i built it with second hand parts which are, cpu:i5 7400 , ram: 8gb ddr4 2400mhz (ram is 1 stick), psu: corsair vs550 (any other part was from my old pc that was tested and 100% work) .
I go to turn on the pc after putting everything together and it turns on for a split second like fans rotate but nothing else and a red light on the bottom right of the motherboard which im assuming isnt good but im not sure on what that means ive tried doing several things like rearranging my ram checked the cpu and made sure everythings plugged in but its still not working.
Can anybody help out?
(Im not sure how to add a photo so im sorry that theres no photo) Number