This is a common problem that occurs with the error message “turn off power and try again”.This usually happens when the camera lens doesn’t retract from the extended position due to the inability of the camera lens to retract. This is usually caused due to a sudden powering down, dropping the camera, or dirt getting into the mechanism.

• You should first replace the batteries and try turning it on again.
• Reset the camera to factory settings. To reset turn off the camera and remove the battery. Hold down the power button for 15 seconds then release. Reinsert the battery pack and power on the camera.
• If that doesn’t work attempt to give the camera a good jolt. A shake of the camera will often realign the mechanism or knock off dirt. 
• Another alternative is to tap the camera with some pressure to forcefully realign the mechanism. This should only be tried as a last case scenario.

 Source : http://www.ifixit.com