That happened on one of mine as well. It is sometimes possible to take a large flathead screwdriver and turn the mechanism with that rectangular hole in the middle, although it can be a little tricky to do. I ended up resorting to tape because it was too much of a hassle. From what I can tell, there isn’t really a way of fixing that unless you replace the entire bottom case, which is a pretty big task and honestly isn’t worth doing for a computer that old, unless it is really important to you. Here is the guide for that: [guide|537]