Aurora R4, won't boot with Asus Pro Art Display

Hi, Bought two Asus Pro Art displays but Aurora R4 will not boot with them attached. It beeps 6 time repeatedly. The issue appears to be a bios problem. I can boot the PC with a different monitor, then swap the monitor to the asus and it works. It just will not boot with it attached.

I had a suggestion here to try a different graphics card. So I upgraded the GTX 760 to a GTX 1070, but the problem  is the same. Now spent €1300 spent on upgrade with nothing working, very frustrating.

Note that the monitors work on my work hewlett packard HP PC, but I need it to work on my Alienware PC.

All connections are DP.

Thanks to the person who helped me last week, but the thread has been moved while I was waiting for graphics card to arrive and I cannot locate the post.