HP monitor is not detected by PC

[DimaU]

I am using HP Z2 Mini G3 Workstation (Windows 10 64) with HP Elitedisplay E221i, connecting it through DisplayPort, and everything works normally there. I am trying to connect the second monitor, which is HP Compaq LA2206x, also through DisplayPort. I am using the cable and the port I used for E221i, hence both the cable and the port are operational. 

Problem: whenever I connect LA2206x, it is not detected by the PC (this holds no matter whether E221i is connected).  LA2206x is not detected in the Device Manager, and whenever I try to search for it in Devices and Printers through "Add new device" button, it is not detected as well. 

Drivers are installed from HP website for this exact monitor (however, on HP website they are available only for Windows 8 64, but not for Windows 10 for some reason, so the drivers installed are the ones for the correct monitor, but for Windows 8 -- please let me know if this can be the sourse of the problem). 

On the monitor LA2206x itself I selected DisplayPort as the default source of signal. Whenever the monitor scans for signal through the ports, it shows "No Signal" for DisplayPort. 

Whenever I unplug the cable from LA2206x while the PC is on, it says "Check Video Cable", which I assume means that the cable is inserted into LA2206x successfully. 

Starting from the sutiation when everything is turned off and LA2206x and the PC are disconnected, I tried all permutations of the following events (if you have an idea about which combination is the most likely one to work, please let me know): 

- turning on the PC 

- turning on the Monitor

- inserting DisplayPort cable into LA2206x

I tried this both for E221i DisplayPort cable plugged and unplugged into PC with the same result. 

This LA2206x was working successfully in the previous configuration. 

I would really appreciate any pieces of advice about how to solve this issue. If any additional info is needed, I would be very happy to provide it.