I have a brand new MacBook Pro (2017 model) and a Plugable USB-C to DisplayPort cable. Plugable cable is connected to DP-in on a Dell U2415. Second cable goes from miniDP-out to second Dell U2415, DP-in. First monitor is configured for DP 1.2 (enabled), second monitor has it disabled. These are the instructions that I have found on the Dell web site.
Plugable describes the cable as supporting MST. Apple says the hardware/software supports MST. But the second display only mirrors the first display. However, the first display is extended from the laptop display.
If I disconnect the Plugable cable and connect a miniDP to DP cable to the first monitor, and change no settings, then connect it to a miniDP port on a windows laptop, MST works fine.
I’m trying to determine if the plugable cable is the culprit, or it if something else. Apple is trying to look into this. Dell tool.
@PlugableSupport – any suggestions?