Question New PC not detecting Monitors and Peripherals

Dec 24, 2020
My brother has recently decided he's going to build his own gaming PC. He has purchased most of the parts as new with a few left over from another PC, they will be listed below.
After working on it for several hours, when it came to power on, everything powered on in the desktop, all fans working etc. yet neither of the two monitors were detecting a signal and it was also not detecting a keyboard and mouse.
I've tried moving the RAM slots around, removing the Graphics Card and still nothing is being detected. The motherboard did come with drivers, but its on a CD (the PC doesn't have a CD drive) and likewise its not detecting the keyboard, mouse and monitors in order for us to interact with the driver loading screen for this to work anyway.
I can't even get into the BIOS, as the keyboard isn't being detected.
Please could someone advise troubleshooting?

Specs are:
Case: Carbid Series Spec 05
Motherboard: Asus ROG Strix Z390-H Gaming
Processor: Intel i7-9700k
Graphics Card: Nvidea RTX-2070 Super
Coolers/Fans: iCue H100i RGB Pro XT
RAM: 2x8GB
Storage: 1x2TB HDD, 1x500GB SSD, 1x128GB SSD

This PC has been built from scratch, so it may be that something is connected in the wrong place.