The first likely problem with the device is a faulty or drained battery. Make sure the battery is completely charged before use, and if that doesn't work, then the battery could be bad.

The power button may be broken and will need to be replaced. The power button may not look broken but the electronic components that relay the message to the motherboard may need to be replaced here.

When you try to focus the camera, it fails to focus or continues to remain blurry.

The most common problem with the camera not focusing is the lenses being scratched or damaged. The lens will most likely need to be replaced because the lens is specifically made and when it scratches it changes the configuration which doesn't allow the camera to properly focus.

If the lenses appears to be fine, then the problem is the most likely the motherboard, and this will need to be replaced here. To fix the motherboard without replacing it requires a fine soldering iron along with equipment to test the circuits components.

The LCD screen is black, or will flicker from being on to black. Turning it off and back on does not fix the issue.

The most likely cause of this happening is that the LCD is broken. A wire may be loose and to check one will need to open up the camera. A replacement guide for this LCD screen can be found here. The motherboard could be at fault and will most likely need to be replaced here.

One or more of the camera buttons on the back of the camera are not working.

The buttons might be broken, which in this case they will need to be replaced. Other components that can be at fault are the motherboard and the LCD control board. A replacement guide for the control board can be found here.

The camera flash does not work either from time to time or all the time, no matter how many times the settings are changed.

Make sure that the battery is not low on power and is almost or completely charged. The flash uses up portions of the battery and needs the battery to have a good portion of life to be used.

If the battery is charged, then the flash itself is bad and will need to be replaced. Other things that can cause this are motherboard and connector issues. A replacement guide for the flash can be found here. It could also be the flash capacitor which the replacement guide can be found here.