There's two kinds of squeakers in toys that I'm aware of- the electric kind, and the plastic dog-toy kind. The electric kind will have hard edges, a noticeable button somewhere on it, and a wire. The plastic kind should feel like a rounded disc, with a small bump on one end.
The electric kind is straightforward- find button, push button. The plastic kind is tricker, as you literally have to squeeze it to force air of out the bump to make the sound. If the angle's wrong or the seal is bad, it won't work.
Get in there with all your fingers and smush the whole thing around- you should be able to isolate the squeaker, feel out what kind it is, and see if it's really broken. If it is, contact LRG for a replacement (assuming it's directly from them and not an Ebay pickup.)