Dell UltraSharp 42.51" 4K Monitor - Manual (Page 75)

Troubleshooting | 75
No HDMI 2 Cable
The display will go into Standby Mode in 4 minutes.
www.dell.com/U4323QE
or
No USB-C Cable
The display will go into Standby Mode in 4 minutes.
www.dell.com/U4323QE
4. This box 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.