Motherboard won't turn on / no post

[dankest_bank]

My first boot attempt, and nothing.
No case fans, no CPU fan, no motherboard LED, no GPU fans

My 24 pin cable is connected securely
My 8 pin cable is connected securely
The switch on the back of the PSU is set to on
The outlet is tested and working
The power cable is tested and working

Whats wrong?? The cpu cooler fan actually turned on with the power supply when I tested it about an hour ago, but now nothing.

R5 1600
Asrock X370 Pro4
16Gb G. skill EVO RAM
Corsair CX550 (2017)
Phanteks p400S

 

[norcalsc]

what GPU?

nevermind you mentioned no gpu fans

 

[dankest_bank]

what GPU?

nevermind you mentioned no gpu fans

Rx 580 8GB

Any ideas??

 

[Obakasama]

The POST sticky has things you can try: http://www.tomshardware.co.uk/forum/261145-31-perform-steps-posting-post-boot-video-problems