Mobo Power Reset switch on but nothing happens

[w1ntervention]

I have just constructed my first build:

1 x Asus X99-S - Intel Core i7 5820K Six Core CPU & Motherboard Bundle ***£30 Saving***
Corsair Vengeance 16GB (4x4GB) DDR4 PC4-19200C14 2400MHz Quad Channel Kit
EVGA GeForce GTX 970 FTW "Plus Edition" ACX 2.0 4096MB GDDR5 PCI-Express Graphics Card
Seagate SSHD 7200RPM 3.5" 1TB SATA 6Gb/s 64MB Cache
Samsung 120GB 850 EVO SSD 2.5" SATA 6Gbps
SuperFlower Leadex GOLD 1000W Fully Modular "80 Plus Gold" Power Supply
NZXT Phantom 410 Enthusiast Midi Tower Case
Alpenföhn Matterhorn White CPU Cooler

When I turn on the power, the motherboard POWER / RESET buttons light up, but nothing else happens, no fans, no q-code, nada.
The heatsink is connected to the CPU fan connector on the motherboard.
THE PLED-, PLED+, HDD LED, POWER SW and RESET SW all connect to the Asus Q-connector which connects to the corresponding connectors on the motherboard.
The front panel USB cable connects to the Asus Q-connector (USB) which connects to the USB connector on the motherboard
The front panel USB 3.0 cable connects to the USB 3.0 connector on the motherboard.
The HD audio connects to the front panel audio connector.
The SSD and SSHD connect with a sata cable to sata connectors on the motherboard.
The motherboard is definitely placed correctly on the standoffs.
The GPU is connected to the PSU by an 8 pin and a 6 pin cable.
The motherboard is connected to the PSU by a 24 pin and 8 pin cable.
The SSD and SSHD are connected to the PSU by a single cable which splits into two sata cables, and two 4 pin molex cables, one of which connects to the 4 pin molex fan.

I've tried using only one stick of RAM.
I've tried without either hard drives.
I've tried pressing the CLR_CMOS button.
I've tried pressing and holding the MemOK! button.

At this point I have no idea what is wrong
Any advice / suggestions would be greatly appreciated.

Thanks.

 

[Karateyid]

Have you tried powering it on using a screwdriver and not the case button? Possible to take it out of case and try powering up in case of a case short

 

[Divine Pain]

When you say you turn on the power, did you mean from the mains socket or the case button?

Did you even try pressing the power button on the edge of the motherboard?

 

[w1ntervention]

That was a super simple fix, and ridiculously embarrassing ^_^
I pushed the case button power button, and everything was working beautifully hahaha. I had tried that much earlier, and nothing had happened that time, started to fiddle, but only tested to see if it worked by pressing the PSU switch rather than the case switch, so of course it looked like nothing was working!
Thanks guys so much