DIAGNOSIS Not broken. The USB hub on the monitor requires a specific data connection to be active. It does not get power from HDMI alone.
FIX You must connect the upstream USB-B cable. Use the included square USB-B to USB-A cable. Plug the USB-B end into the monitor's upstream port. Plug the USB-A end into your computer. This activates the side USB ports and the Ethernet port.
IF THAT DIDN'T WORK Check the monitor's OSD menu. Press the joystick. Go to Menu > USB > USB Hub. Ensure it is set to On. Also, try a different USB-A port on your computer.
HEADS UP The USB hub only works when the monitor is on. It will not charge devices or transfer data when the monitor is in standby or off.