PC won't boot from pen drive (Z170M-D3H)

[oRISHi]

Hi. I've recently build a computer for my brother, these are the specs:
Intel Core i5-6400
Gigabyte Z170M-D3H
8GB RAM Gskill Aegis 2400mhz
1TB Western Digital Black

I've updated the BIOS to F7, the last one for this board. The main problem is that it can't boot from any pen drive. I press F12 at startup screen, select my USB device, but then it doesn't even reach to the Clover boot options, it just shows me the BIOS Boot Manager, like in this picture:

Then, when I select "Boot Manager", the only option that appears is "EFI Hard Drive". At this instance it also should say "EFI USB Device", to boot from the pen drive, but it doesn't. Selecting "EFI Hard Drive" and pressing enter doesn't do anything.

I'm confused because the pen drive is eligible from the BIOS boot options, it displays it's information correctly, but the Boot manager doesn't allow me to boot from the USB device. I've tried with a pen drive created with Unibeast for El Capitan, and another one created for Yosemite. Both of them work well on other PCs (I can boot to the installer screen). I've also tried with every USB port on the motherboard, 2.0 and 3.0, and the results are the same.

What should I do?
Thanks in advance.

 

[oRISHi]

Ok, I solved this issue by reinstalling Clover to the USB drive in UEFI mode, before it was installed as Legacy Boot. Now I'm able to reach the Clover screen, where I select verbose boot and after a few minutes this Kernel Panic comes up:

Any ideas?

 

[P1LGRIM]

Any ideas?

Disable the freakin' Serial port (SuperIO)

 

[VioletDragon]

Ok, I solved this issue by reinstalling Clover to the USB drive in UEFI mode, before it was installed as Legacy Boot. Now I'm able to reach the Clover screen, where I select verbose boot and after a few minutes this Kernel Panic comes up:

Any ideas?

It is know that having Serial Port enabled in the BIOS to cause kernel panics with IOBluetoothHostController. As P1LGRIM says disable Serial Port.