Took delivery yesterday of two U2723QE. Set up per instructions for "Connecting the Monitor for USB-C Multi-Stream Transport (MST) Function" on page 42 of User's Guide. 

First tried with both U2723QE attached by MST daisy chain. USB-C from laptop to upstream USB-C input on U2723QE 1. (Input #8 per manual page 12). Black screen on both, with response "USB-C not found".

Next separated the monitors and independently connected to input #8. Both gave black screen.

Next used a different laptop (12 month old Dell XPS). Same problem.

Next swapped out the Dell provided USB-C cables (tried both) with a Thunderbolt 3 cable. Same problem.

Next attached Thunderbolt from PC to a downstream USB-C port on monitor 1. BRAVO! It worked. And daisy chain also worked to monitor 2.

BUT (there's always a BUT) the hub function of the screens don't work. None of the USB-1 ports are active. No surprise, because there is no connection from PC to the upstream USB input on the monitor. So I added a second USB-C to USB-C cable from PC to upstream port #8. Made no difference. The daisy chain video continues to work, but not the hub functionality.

HELP! Is it really possible the Dell has shipped two new monitors, both with faulty upstream USB-C input ports? Or am I missing something?