What might cause my camera not to work? (It doesn't turn on at all)

[Waddizzle]

No battery has been installed, for one. 

Dropping the camera on the floor is another possiblity that could cause it to not turn on.

[edmondexpo]

Is there any way I could fix it myself? Or should I take it in?

[Waddizzle]

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@edmondexpo wrote:

Is there any way I could fix it myself? Or should I take it in?

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Judging from your descriptions of the issue, I doubt that you'd be able to fix it.  Have an expert look at it.

[edmondexpo]

My battery is healthy.

[TCampbell]

There are two micro-switches... one on the battery compartment door and one on the memory card door.  If they are not engaged (doors closed) then the camera will not power up.

Check that the doors close properly and are undamaged.