Hi David. Welcome to justanswer.
This is usually caused by sand or grit interfering with the lens extension mechanism, or the camera's been dropped with the lens extended. It is also possible that the camera has been powered on, but the lens had been blocked preventing its extension.
Remove the batteries from the camera, wait a few minutes. Put a fresh set of batteries back in and turn the camera on.
If new batteries didn't work, try pressing and holding the Menu, Function, Function Set, or OK button while turning the camera on.
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Reply if still the problem is there