We've had a few customers call us thinking that the battery cover was broken, only to find out it was actually just not installed correctly after putting the battery in.So here are a few tips on the best way to put in the battery and then the cover:
1)  We recommend that you put the battery (be sure to take off the clear plastic cover first) into the monitor with the battery terminals near the bottom of the unit (opposite end of the On/Off/Volume dial) and with the battery wires on the right side between the clip and the inside wall. With the battery wires on the side, and not under the battery, the battery will sit lower and allow the cover to snap closed easier.2)  Now take the nose end of the cover (the end nearest the On/Off/Volume dial), hold it at a 45 degree angle to the monitors body and put it in the hole.3)  Slide the cover down towards the bottom until it stops while keeping it at a 45 degree angle.4)  Now lay the cover flat on the body with the 3 other tabs in the holes. There should be a slight gap at the top of the cover.5)  Now slide the cover towards the On/Off switch until it snaps into place and the gap is closed.
If this hasn't resolved the problem then feel free to reach out to us at Customer Service.