Complete power failure points to the power connection or adapter.
First, inspect the power cord and adapter for physical damage. Look for frays, cuts, or a bent connector. If the power connector fails or frays, you must stop using it and contact qualified service.
Next, trace the entire path. Unplug the power adapter from the wall and from the monitor. Firmly reconnect it at both ends. The wall socket should be easily accessible. Do not use a power strip or extension cord if possible, as overloading can cause failure.
If that didn't work: Try a different, known-working power outlet. The monitor's power input is 100-240V, so standard household outlets are fine. If there's still no sign of life with a different outlet and cable, the internal power supply or a component has likely failed.
Heads up: Do not attempt to repair it yourself. Opening the unit exposes you to high voltage risks. If the product is dropped, damaged, or shows no power, refer all servicing to qualified service personnel.