Diagnosis
The monitor is receiving power and a signal, but the LCD panel backlight is not illuminating. This is most often caused by the monitor's HDR or Brightness Intelligence Plus (B.I.+) feature conflicting with a source signal.
How to Fix It
First, disconnect all video cables. Power cycle the monitor. Reconnect only one cable. Press the joystick to open the OSD. Navigate to Picture > HDRi and set it to Off. Navigate to Picture > Brightness Intelligence and set it to Off. Your image should return.
If That Didn't Work
The monitor may be stuck in a low-power mode from a prior signal failure. Perform a factory reset. With the monitor on, press and hold the joystick for 10 seconds until the OSD menu appears and disappears. The monitor will reset.
Heads Up
If the screen remains black after these steps, test with a different, known-good DisplayPort or HDMI cable. A faulty cable can cause a handshake failure that manifests as a black screen with audio.