Question DXE_READY_TO_BOOT

[mavelstein]

I just completed the build with asrock TRX40 TAICHI ATX sTRX4 Motherboard . It has a built in BIOS error code display which translates to DXE_READY_TO_BOOT. I am trying to boot from a memtest x86 USB drive.
I have connected external monitor via HDMI on my graphics card but see nothing on my screen.
What can I attempt next ?

 

[rgd1101]

full system spec? include make and model of the psu