new pc build - lights up all component but no display

Dec 11, 2018
hello, I am trying to help a friend states away put his computer together but once we've plugged everything in there is no display showing up on the monitor and no beeps or sound to see if we got in to the bios(even though the display isn't coming on too). we've tried plugging hdmi into the gpu and the motherboard but still can't see anything, also tried using 1 ram stick only... I have no idea what went wrong but everything is lighting up all the front panel connectors are connected, it turns on, all fans are working, but nothing shows up on screens, and we even tried changing hdmi cords. so far we've plugged the gpu in to the pci1 slot and pci3 slot, nothing.. does anyone have any idea what to do ? thanks

I-8700K CPU
asus prime z370a MOBO
corsair vengeance 16g RAM
gigabyte 1080ti aorus 11gb GPU
rosewill glacier 850 80+ bronze PSU
2tb western dig HDD
and noctua NHD15 CPU Cooler