DIAGNOSIS The monitor is receiving power but not a valid video signal from any input. The most likely cause is the monitor's input source not matching the active cable or a cable/GPU handshake issue.
FIX First, manually select the correct input source. Press the monitor's rear joystick. Navigate to and select the 'Input Select' menu. Choose the specific port you are using (e.g., DisplayPort 1, HDMI 1). If the signal returns, the Auto Input Select function failed. Second, power cycle the entire chain. Turn off the monitor and PC. Unplug the monitor power cord for 60 seconds. Reconnect power, turn on the monitor first, then the PC.
IF THAT DIDN'T WORK Test with a different, high-quality certified cable. For DisplayPort, ensure the cable is fully seated; the connector has a latch. Try a different video output port on your graphics card. On your PC, boot into Safe Mode to load basic display drivers, then restart normally to force a fresh handshake.
HEADS UP If using a docking station or adapter, connect the monitor directly to the computer's video output to rule out the intermediary device as the fault. The monitor itself rarely fails; the issue is almost always source or cable related.