My new computer won’t turn on, GPU just blinks

Just assembled my first computer and when I try to turn it on the gpu just blinks a red light for a second on the GIGABYTE led display and nothing happens.

My psu has a voltage selector and I'm almost certain that I chose the correct one (my house has 110v and the selector is at 115v).

I double checked the case buttons connectors and they are in their places .

I also have a thermaltake fan controller connected directly to the psu and it does not turn on either.

Here is a photo of the computer (sorry for the bad cable management, this is my first computer assembled):

Here is the motherboard without the gpu and second push fan on radiator:

The ATX cable is connected to the motherboard behind the radiator in the top left of the image.

My computer specs:

• Motherboard ASUS B150M-C/BR
• Gigabyte GEForce GTX 1060 windforce
• Intel core i5 6600k
• PSU Xigmatek Calibre 600w
• Case corsair carbide spec-03
• Corsair hydro cooler h55
• SSD 500GB and 2TB + 160GB HDD
• 8GB RAM Kingston DDR4

PS: I tried to turn it on without the PCI-E cable connected to the GPU and it still blinks red and turn off
PS2: Just made the paper clip test on the psu and it doesn't start the fan. It may be the source of the problem, but why my GPU flashed red before?

I'm open to suggestions and I can perform tests.

Thanks in advance

EDIT: The solution was reinserting all motherboard psu connectors and RAM and forcing them a little more inside.
Thanks for everyone that helped!