Go into the BIOS settings, make sure that the option for graphics output is set to “IGPU”, so that the processor is outputting the graphics, and then plug the monitor cable into the motherboard output. If any cards are not detected, then the fault is either the card, riser, or motherboard port.
The problem you may have been facing is the motherboard automatically making the video output set to the graphics card, instead of to the CPU.
To diagnose any other issues, look at the EZ Debug LEDs, (Page 39 in manual) about what component is causing the problem in the startup sequence.
The last possible problem would be the output ports on each end of the displays/ the cable, but that would be obvious from just looking at either end, and seeing any bent pins/exposed wires, as you are working with an analog signal.
Make sure you are running the latest driver version for your gpu
make sure windows has all of its updates
Did you follow the instructions from the mining software which says to:
expand your virtual memory to 16GB?
and
Set the following environment variables: