The answer to 'light fixture not working' is that there are several common causes, including a blown fuse or tripped circuit breaker, a faulty light bulb, loose or damaged wiring, or a problem with the light fixture itself. Symptoms may include the light not turning on at all, flickering or intermittent operation, or the light being dim.
If the issue is a blown fuse or tripped breaker, you can try resetting the breaker or replacing the fuse. If it's a faulty bulb, simply replace the bulb. For issues with wiring or the fixture, it's generally best to call a licensed electrician, as electrical work can be dangerous if not done properly.