When a system is connected to a monitor via a USB connection only (instead of VGA, DVI, DisplayPort etc.), the following error will appear if the Dell Display Monitor (DDM) application is launched (Figure 1):
Figure 1: Dell Display Manager Error
The Dell Display Manager application relies on Display Data Channel (DDC) information. This information is not passed through a USB connection.
In order to get the Dell Display Manager application to work correctly, the monitor must be connected a digital DDC-supported video cable like DVI-D, DVI-I, HDMI, DisplayPort (DP or mDP), or USB-C (that supports DisplayPort or Thunderbolt 3).