Pc wont turn on

[winged arch]

Building my pc and when i press the button no power is going to the pc. Theres a light on my montech xr that is red for i think hdd. but I press on switch on pc and it doesnt work

https://uk.pcpartpicker.com/list/f2Fn4p

my parts list

[winged arch]

I think its the motherboard

I have checked the psu and it is fine

How to I check

[lunar coral]

are you pressing the button on the case