Computer shutting off as I start it

[Len]

So,

something really weird,

Finished building my comp like 2 weeks ago,
and never had the time to completely finish everything up, busy as hell, and when I have some free time I'm just exhausted..

So anyway,

My gf prolly threw away my original 5pin cable to sata power for the HDD's and SSD,
And I tried buying 2 spare ones, which none of them worked.. I figured they're all the same,
and apparently, they are not.
I have a full modular PSU (SeaSonic 560w X Series 80+ Gold)

i7 7700 Kaby Lake
GTX 980TI G1 Gaming
H110m-K
HyperX Fury 8gb 2133mhz x2

So I've tried installing both of the cables (5 pin to sata power), the first one required some pushing to plug in,
which was kind of suspicious, so after 2 tries, i've stopped trying it, and i went to a shop and bought another one,
Now this one fit in just perfectly, but it still didn't work, I plugged it out, and saw that the shapes on the cable itself are different than the ones on the PSU (the pins),
So now I'm trying to understand what the fuck to do.
Because, for some reason my Computer won't start now, when I hit power it just starts and poof, goes right off, like something is causing a short circuit or whatever it's called.

I've tried taking the Battery out of the MOBO and discharge all the power, and then put it back,
but it didn't really do anything.

Is it possible I have destroyed my PSU?
or, what am I missing here ?

This is the first time I am building after like 10-11 years..

If anyone could help me out somehow with this thing,
I'd be most grateful.

Thanks in advance,
Eli.

[Sorshen]

Try starting it with only one ram module and no sata/usb devices.
Did you flash the bios for Kaby Lake support? The mobo probably didn't come out-of-the-box with the latest version. If you didn't/don't know, you'll need to borrow a Skylake cpu to do it. Also check if you plugged in the 4pin cpu power.

[Lathais]

So, this cable is the one that goes from the PSU to the HDD/SSD? On modular PSUs, that cable usually has to be the one supplied with the PSU or custom made for that PSU. Not just any old cable will work sadly.

[Len]

Yeah, I've updated the BIOS already @Hextor, I'm way past that..

I'm guessing non-original cables won't do.. I don't know anymore

I've tried 2 different cables, and they didn't work..

But that doesn't solve the fact my computer won't start now..

I've got no SATA connected whatseoever.. only the CPU, MOBO and fans connected,
I took the GPU cause I was afraid it'll burn or something.