If the P2723DE has an on-board USB hub, then there should be a up-stream USB-cable that must be connect to the computer itself (before it and its USB-ports will work).
Hello everyone, I have XPS 8950 desktop joined with P2723DE monitor. I want to use Logitech C922 webcam with it. Which USB port on the P2723DE should I use out of the 4 ports? PC doesn't detect the webcam when connected to any of these ports on the P2723DE? It works perfectly fine when connected to the back of the XPS. I prefer to keep it connected to the monitor. Is there a way I can make it work? Thanks.   
XPS 8950, Logitech C922 webcam not detected on P2723DE