Year old PC build just stopped over night

[lowonammo20.10]

So i built a PC July last year, its worked completely fine right up until yesterday where the machine wouldn't turn on and the red light flashes for the cpu on my motherboard (MSI 7978 015R Gaming M3 Motherboard Intel H170 S1151). The CPU fan is working, the other 2 fans stop and start as if the machine is trying to start up between flashes but is failing. I removed the heatsink and checked the CPU and nothing seems out of place (I am aware i must re-apply thermal paste now). I've read it could be PSU related but I'm not sure, is it normal for it to just fail over night? Any help would be appreciated.

 

[RARRAF]

PSU make and wattage