The cable is good. If I connect first on built in HDMI connector, and second screen is a display port, display port is works as an extended (only one monitor, LG 29MA73D-PZ, knows PIP, DP 1.2 off mode).
If the first monitor is an LG Ultrawide on built in HDMI, second is a laptop built in screen, works well. But after I attached on the display port a monitor, the built in screen resolution set to low resolution and HDMI switch off... and display port monitor is a blank with no signal. It seems any driver error.
(If I use only display port monitor (no built in hdmi, no built in laptop screen),display port is a blank screen with a no signal. This is my main problem. I have enough one monitor but need it on the display port.)