DIAGNOSIS The monitor is powered on but not receiving a valid video signal from your PC or console. The most likely cause is an HDMI handshake failure or a loose connection.
FIX Follow this sequence. One: Power cycle the monitor. Unplug its power cord for 60 seconds. Two: Ensure the HDMI cable is firmly seated at both the monitor and source device. Three: On the monitor, use the joystick button to open the OSD. Navigate to Menu > System > Reset. Select it. This clears any internal setting conflicts.
IF THAT DIDN'T WORK Test a different, known-good HDMI cable. If available, test the monitor with a different source device (e.g., a game console). This isolates the problem to the monitor, the cable, or your original PC.
HEADS UP If using a desktop PC, try connecting to a different GPU port. Some monitors fail to handshake with specific output ports, especially after a graphics driver update. The monitor's HDMI port is not hot-swap robust; always connect cables with both devices powered off.