If you see a small hole at the bottom of the monitor, use a pen or paper clip to hold the button inside the hole. You will hear 7 beeps followed by a longer beep. Once the longer beep finishes, release the reset button.
If you don’t see a small hole, the monitor is the older version. Follow these steps.
1. Use a screw driver to open the box.
2. Disconnect the batteries. Wait for 2 minutes.
3. Hold the reset button.
4. While holding the reset button, connect the batteries and you should hear a long beep.
If that still doesn’t factory reset the device, follow this video.