PC finished and nothing happens. Help!

[Questionare101]

I just built my first brand new pc. After all the hours of trial and error with the case and cable management, I thought "this is finally it, this is the moment." I turned the psu on and.... nothing happens. I started to think "Did a damage the motherboard, or screw in something too tight?". I don't know why my pc isn't starting up, but any suggestions? Hope I don't have to get another mobo! 

 

PS. The power supply does work and to my knowledge all cables were put in.  

 

My Specs: 

 

Montech Flyer Black mATX case

Ryzen 5 2600X w/stock cooler

WD Blue 7.2K RPM HDD

WD Black Sn750 500gb SSD

GTX 1070 

3 3-pin case fans

Aresgame 650w psu bronze-certified 

Asrock b450m pro4 am4 mATX mobo