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 inserting a sharp pin into the reset hole at the back of the parent unit (underneath the kickstand) and holding for 10 seconds.