Your camera gear is broken, or might be broken, or you're worried something might break it.
Before asking why your camera won't turn on, or your lens won't focus, try the obvious things:
- are batteries charged?
- take the batteries out, check for corrosion, reinsert them
- if your camera has a system reset (most do) try resetting to factory settings
- if you have interchangeable lenses, try removing the lens, cleaning the contacts, and firmly re-seating it
- if you're not sure if the problem is the camera or the lens/flash, try another lens/flash to narrow down if it's the camera body or
When asking questions, make sure you mention everything you've already tried.