Computer won't Turn Off after windows shutdown

[luneki]

I just finished building my dad a new PC, installed windows 10 and all updates are installed.
But when i want to turn off the computer, windows shuts down, the screen goes black and then the PC stays on.
Same thing happens when it tries to reboot, it doesn't restart the PC, just stays on with the black screen.
The build is:

I5 6500
16 GB DDR4 2400
240 GB Kingston SSD
1 TB WD HDD
Asus Sabertooth Z170S

Already tried clearing the CMOS but nothing happened.
Another thing I checked was the fast startup option, but it's not even available under the power button options.
Hibernate is disabled.

What could be happening?

 

[Colif]

have you got latest bios? There might be a setting in BIOS stopping PC from shutting down.
What PSU do you have? Is it win 10 compatible? Does it support the new power modes?

If hibernate was turned off before you looked for fast startup, that is why its not there... it uses hibernate and can't work without it. Anyway, that is not cause of the problem.

Did it do this right from start? Or did it just start after windows was loaded? If second, try a clean boot and see if it changes anything:
https://support.microsoft.com/en-us/kb/929135
that will tell you if its possibly windows or a program that loads at start up

 

[Luuk__]

Does the system have a GPU? So yes, is the HDMI/VGA Cable connected to the GPU? Did you try booting it without the GPU?

 

[luneki]

have you got latest bios? There might be a setting in BIOS stopping PC from shutting down.
What PSU do you have? Is it win 10 compatible? Does it support the new power modes?

If hibernate was turned off before you looked for fast startup, that is why its not there... it uses hibernate and can't work without it. Anyway, that is not cause of the problem.

Did it do this right from start? Or did it just start after windows was loaded? If second, try a clean boot and see if it changes anything:
https://support.microsoft.com/en-us/kb/929135
that will tell you if its possibly windows or a program that loads at start up

I updated the BIOS to the latest one and nothing. I have a Corsair CX450m.

It did it since the start, while it was installing windows it had to reboot, but didnt restart, so i had to turn it off with the button and back on again to continue the installation.
I checked all over the BIOS settings but didn't find anything relevant to this, at least to my knowledge.