This could be a simple problem with a simple fix. First make sure the device is clean and free of dirt and dust. This is the most likely reason the touchscreen isn’t functioning properly. If the device is clean and still is unresponsive, perform a touchscreen-free factory reset of the device detailed in the troubleshooting guide. If a factory reset is unsuccessful, the screen may need to be replaced. Visit this Troubleshooting Page for help with the above and more answers.