Diagnosis
The monitor is receiving power but not detecting an active video signal from your PC through the selected input.
How to Fix It
First, verify the source device is powered on and sending video. Then, manually cycle the monitor's input source. Press the physical joystick button on the back-bottom bezel. Navigate to the 'Input Select' menu. Toggle from HDMI 1 to HDMI 2 or DisplayPort, then back. This forces a fresh signal handshake. Ensure the cable is fully seated at both ends.
If That Didn't Work
The issue may be a power-saving mode conflict. Disconnect the monitor's power cable from the wall or surge protector for 60 seconds. Reconnect it. This clears the monitor's internal state. Simultaneously, restart your PC to reinitialize its graphics driver handshake.
Heads Up
If the problem persists only with a specific device, test with another known-good HDMI cable. Faulty or out-of-spec cables are a frequent point of failure for the 2K resolution handshake.