new pc won’t post

hi,

so i just built my first pc like 10 minites ago, tried to get it to boot but it won’t. im using a b450 and a 2700 for good measure (i have a 3900x, just wanna update bios) + 2060 only a 500w psu (everything else was out of stock). i’ve tried switching ram slots and taking 1 ram out. i’ve checked cables 2x and everythings plugged in properly, everything that has light, does have light (graphics card, ram, front io). i’ve tried everything i know and just really need help.

best regards,

cider

p.s ; my mouse which if plugged in on a turned of pc, also doesn’t flash rgb

1 ; tried with a diffrent graphics card. same outcome.