Nothing on the display

Helping my son build his first PC it’s been about 20 years since I have built one from scratch. Got everything plugged in and sorted out except for the NVME which is still waiting to arrive.

Turn it on case lights and fans come on but nothing appears on the displays to indicate it is booting to bios and displays says no signal. i figured it would boot to bios and say no boot device found

Any ideas why that would be Or should I just wait until the NVME arrives to try again