Dell P2723QE 27" 4K UHD USB Type-C Hub Monitor - Manual (Page 71)

Troubleshooting │ 71
4. This message also appears during normal system operation, if the video cable
becomes disconnected or damaged.
5. Turn Off your monitor and reconnect the video cable; then turn On both your
computer and the monitor.
If your monitor screen remains blank after you use the previous procedure, check your
video controller and computer, because your monitor is functioning properly.