Please ensure the monitor is not in Audio Only Mode, which is activated by briefly pressing the power button.
- Switch between the power adapters of the camera and parent units and let the parent unit charge for a while before turning it back on.
- If that solved the issue, then the problem is with the power adapter.
- If the issue persists, disconnect the cameras and parent unit from the power adapters, try to reset the monitor by opening the battery compartment, disconnecting the battery sack from the connection port, waiting for 2 minutes and reconnecting the battery.