Dell UltraSharp U3415W User Manual page 60

or
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.
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| Troubleshooting