Newly Built pc won’t turn on

So I just finished building my pc but it won’t turn on. Everything seem in place, standoffs are in, but nothing. Tested the psu with the paperclip thing and it worked. Please help I cant figure out why it doesn’t work. Specs : Motherboard msi b550 gaming gen3 Psu msi mag a650bn Cpu ryzen 5 5600 Gpu rx6700xt Ram g skill aegis ddr4 2x16 Case msi mag forge a120 flow