I didn't think to try a different monitor, but I did try the monitor with both a HDMI and a DP cable.
All I can say is, who would have thought that building an integrated curcuit onto a silicon wafer with over 10,000,000 7nm transistors would be so difficult.
I think I tried both HDMI and DVI on the 23" (no DP), but it worked fine with HDMI on my 34". Both monitors are manufactured by 'Philips' (actually Top Victory Electronics)