An Issue with HP Z27k G3 Monitor Display Port Connectivity

[z27g3user]

My HP Z27k G3 monitor has ceased to function properly in Display Port v.1.2 and v.1.4 modes, only allowing Display Port v.1.1 to work.

I have conducted thorough testing with different workstations to isolate the problem.

When connected to my HP Z2 Mini G3 workstation with i5-6500 Intel® HD Graphics 530, capable of supporting 3840x2160@60Hz over Display Port, I could only achieve 3840x2160@30Hz in Display Port 1.1 mode, both on Linux and Windows operating systems. After switching to DP1.2 or 1.4, the driver tries to set 60Hz and connection to monitor is lost. In fact, xrandr reports 3840x2160@60Hz mode for Display Port, so it is not likely a driver issue.

Similarly, when connected to an older HP Z400 workstation with an NVIDIA Quadro K2000 adapter, which also supports 3840x2160@60Hz, only Display Port 1.1 mode functioned. When I set DP 1.2 or 1.4 mode in the monitor menu, it becomes blank and says that there is no input signal.

In an attempt to troubleshoot the issue, I purchased two new 4k@60Hz compatible Display Port cables (namely HP 917463-003 and HP 917463-001) and even tried a DP-to-HDMI 2.0 cable, but unfortunately, the problem persisted in all combinations of hardware and software. Save perhaps the USB input, since I do not have a compatible device to check it out. But both DP and HDMI did not work at 60Hz. Based on these tests, it appears that the issue lies with the monitor itself.

Resetting monitor settings changed nothing.

I must emphasize that I hold a great appreciation for this monitor, as well as other HP products, so any suggestions are welcome. I think I remember that it refused to set 60Hz mode a couple of times after a cold boot few weeks ago, but worked well after reboot. Does the monitor have some sort of debug interface, logs or other diagnostic tools to see what happens inside?