First, inspect the display for any cracks or chips. If you notice lines or visible cracks in the glass or the display underneath the glass, chances are you will need to replace the entire display.
If you don’t notice any immediate damage to the screen and the device is clearly powered on, the next step will be to take apart the device and check for any loose cables. There may be a loose or worn cable connecting the display that will need to be replaced or tightened.
In either case, you will need to take apart the device and gain access to the display. Please check out our troubleshooting page for more information on how to do this.