Make sure you fully insert the tab. Then press the bumper insert all the way down until it snaps into place. At first I thought it was locked but it wasn't, be careful. It should click into place. I would crawl under the car and make sure. There are two latches. My bottom one snapped normally, but the top one didn't snap at all. However, it looks pretty reliable. EDIT: I ended up securing the insert by drilling a hole in the "fin" on the back and threading a zip tie through the hole and a handy hole in the body. Now it's going nowhere.