I'm not really familiar with a lot of these smaller safes, but I recall reading somewhere where some of these safes used a small electric motor with a short cable attached to open the latch. This cable would often break or become disconnected.
Regardless of what the problem is, you can probably take it apart to take a look. Most of this stuff is designed to be disposable. Once it breaks you're supposed to throw it away and buy a new one.
